PERLDELTA(1) Perl Programmers Reference Guide PERLDELTA(1)NAMEperldelta - what's new for perl v5.6.x
DESCRIPTION
This document describes differences between the 5.005
release and the 5.6.1 release.
Summary of changes between 5.6.0 and 5.6.1
This section contains a summary of the changes between the
5.6.0 release and the 5.6.1 release. More details about
the changes mentioned here may be found in the Changes
files that accompany the Perl source distribution. See
the perlhack manpage for pointers to online resources
where you can inspect the individual patches described by
these changes.
Security Issues
suidperl will not run /bin/mail anymore, because some
platforms have a /bin/mail that is vulnerable to buffer
overflow attacks.
Note that suidperl is neither built nor installed by
default in any recent version of perl. Use of suidperl is
highly discouraged. If you think you need it, try alter
natives such as sudo first. See http://www.courte
san.com/sudo/.
Core bug fixes
This is not an exhaustive list. It is intended to cover
only the significant user-visible changes.
""UNIVERSAL::isa()""
A bug in the caching mechanism used by "UNIVER
SAL::isa()" that affected base.pm has been fixed. The
bug has existed since the 5.005 releases, but wasn't
tickled by base.pm in those releases.
Memory leaks
Various cases of memory leaks and attempts to access
uninitialized memory have been cured. See the Known
Problems entry elsewhere in this document below for
further issues.
Numeric conversions
Numeric conversions did not recognize changes in the
string value properly in certain circumstances.
In other situations, large unsigned numbers (those
above 2**31) could sometimes lose their unsignedness,
causing bogus results in arithmetic operations.
Integer modulus on large unsigned integers sometimes
returned incorrect values.
Perl 5.6.0 generated "not a number" warnings on cer
tain conversions where previous versions didn't.
These problems have all been rectified.
Infinity is now recognized as a number.
qw(a\\b)
In Perl 5.6.0, qw(a\\b) produced a string with two
backslashes instead of one, in a departure from the
behavior in previous versions. The older behavior has
been reinstated.
caller()caller() could cause core dumps in certain situations.
Carp was sometimes affected by this problem.
Bugs in regular expressions
Pattern matches on overloaded values are now handled
correctly.
Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to
spurious warnings. This has been corrected.
The RE engine found in Perl 5.6.0 accidentally pes
simised certain kinds of simple pattern matches.
These are now handled better.
Regular expression debug output (whether through "use
re 'debug'" or via "-Dr") now looks better.
Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were
flawed. The bug has been fixed.
Use of $& could trigger a core dump under some situa
tions. This is now avoided.
Match variables $1 et al., weren't being unset when a
pattern match was backtracking, and the anomaly showed
up inside "/...(?{ ... }).../" etc. These variables
are now tracked correctly.
pos() did not return the correct value within s///ge
in earlier versions. This is now handled correctly.
""slurp"" mode
readline() on files opened in "slurp" mode could
return an extra "" at the end in certain situations.
This has been corrected.
Autovivification of symbolic references to special vari
ables
Autovivification of symbolic references of special
variables described in the perlvar manpage (as in
"${$num}") was accidentally disabled. This works
again now.
Lexical warnings
Lexical warnings now propagate correctly into "eval
"..."".
"use warnings qw(FATAL all)" did not work as intended.
This has been corrected.
Lexical warnings could leak into other scopes in some
situations. This is now fixed.
warnings::enabled() now reports the state of $^W cor
rectly if the caller isn't using lexical warnings.
Spurious warnings and errors
Perl 5.6.0 could emit spurious warnings about
redefinition of dl_error() when statically building
extensions into perl. This has been corrected.
"our" variables could result in bogus "Variable will
not stay shared" warnings. This is now fixed.
"our" variables of the same name declared in two sib
ling blocks resulted in bogus warnings about "redecla
ration" of the variables. The problem has been cor
rected.
glob()
Compatibility of the builtin glob() with old csh-based
glob has been improved with the addition of
GLOB_ALPHASORT option. See "File::Glob".
File::Glob::glob() has been renamed to
File::Glob::bsd_glob() because the name clashes with
the builtin glob(). The older name is still available
for compatibility, but is deprecated.
Spurious syntax errors generated in certain situa
tions, when glob() caused File::Glob to be loaded for
the first time, have been fixed.
Tainting
Some cases of inconsistent taint propagation (such as
within hash values) have been fixed.
The tainting behavior of sprintf() has been rational
ized. It does not taint the result of floating point
formats anymore, making the behavior consistent with
that of string interpolation.
sort()
Arguments to sort() weren't being provided the right
wantarray() context. The comparison block is now run
in scalar context, and the arguments to be sorted are
always provided list context.
sort() is also fully reentrant, in the sense that the
sort function can itself call sort(). This did not
work reliably in previous releases.
#line directives
#line directives now work correctly when they appear
at the very beginning of "eval "..."".
Subroutine prototypes
The (\&) prototype now works properly.
map()map() could get pathologically slow when the result
list it generates is larger than the source list. The
performance has been improved for common scenarios.
Debugger
Debugger exit code now reflects the script exit code.
Condition ""0"" in breakpoints is now treated cor
rectly.
The "d" command now checks the line number.
"$." is no longer corrupted by the debugger.
All debugger output now correctly goes to the socket
if RemotePort is set.
PERL5OPT
PERL5OPT can be set to more than one switch group.
Previously, it used to be limited to one group of
options only.
chop()
chop(@list) in list context returned the characters
chopped in reverse order. This has been reversed to
be in the right order.
Unicode support
Unicode support has seen a large number of incremental
improvements, but continues to be highly experimental.
It is not expected to be fully supported in the 5.6.x
maintenance releases.
substr(), join(), repeat(), reverse(), quotemeta() and
string concatenation were all handling Unicode strings
incorrectly in Perl 5.6.0. This has been corrected.
Support for "tr///CU" and "tr///UC" etc., have been
removed since we realized the interface is broken.
For similar functionality, see the pack entry in the
perlfunc manpage.
The Unicode Character Database has been updated to
version 3.0.1 with additions made available to the
public as of August 30, 2000.
The Unicode character classes \p{Blank} and
\p{SpacePerl} have been added. "Blank" is like C
isblank(), that is, it contains only "horizontal
whitespace" (the space character is, the newline
isn't), and the "SpacePerl" is the Unicode equivalent
of "\s" (\p{Space} isn't, since that includes the ver
tical tabulator character, whereas "\s" doesn't.)
If you are experimenting with Unicode support in perl,
the development versions of Perl may have more to
offer. In particular, I/O layers are now available in
the development track, but not in the maintenance
track, primarily to do backward compatibility issues.
Unicode support is also evolving rapidly on a daily
basis in the development track--the maintenance track
only reflects the most conservative of these changes.
64-bit support
Support for 64-bit platforms has been improved, but
continues to be experimental. The level of support
varies greatly among platforms.
Compiler
The B Compiler and its various backends have had many
incremental improvements, but they continue to remain
highly experimental. Use in production environments
is discouraged.
The perlcc tool has been rewritten so that the user
interface is much more like that of a C compiler.
The perlbc tools has been removed. Use "perlcc -B"
instead.
Lvalue subroutines
There have been various bugfixes to support lvalue
subroutines better. However, the feature still
remains experimental.
IO::Socket
IO::Socket::INET failed to open the specified port if
the service name was not known. It now correctly uses
the supplied port number as is.
File::Find
File::Find now chdir()s correctly when chasing sym
bolic links.
xsubpp
xsubpp now tolerates embedded POD sections.
""no Module;""
"no Module;" does not produce an error even if Module
does not have an unimport() method. This parallels
the behavior of "use" vis-a-vis "import".
Tests
A large number of tests have been added.
Core features
untie() will now call an UNTIE() hook if it exists. See
the perltie manpage for details.
The "-DT" command line switch outputs copious tokenizing
information. See the perlrun manpage.
Arrays are now always interpolated in double-quotish
strings. Previously, ""foo@bar.com"" used to be a fatal
error at compile time, if an array "@bar" was not used or
declared. This transitional behavior was intended to help
migrate perl4 code, and is deemed to be no longer useful.
See the Arrays now always interpolate into double-quoted
strings entry elsewhere in this document.
keys(), each(), pop(), push(), shift(), splice() and
unshift() can all be overridden now.
"my __PACKAGE__ $obj" now does the expected thing.
Configuration issues
On some systems (IRIX and Solaris among them) the system
malloc is demonstrably better. While the defaults haven't
been changed in order to retain binary compatibility with
earlier releases, you may be better off building perl with
"Configure -Uusemymalloc ..." as discussed in the INSTALL
file.
"Configure" has been enhanced in various ways:
Minimizes use of temporary files.
By default, does not link perl with libraries not used
by it, such as the various dbm libraries. SunOS 4.x
hints preserve behavior on that platform.
Support for pdp11-style memory models has been removed
due to obsolescence.
Building outside the source tree is supported on sys
tems that have symbolic links. This is done by running
sh /path/to/source/Configure -Dmksymlinks ...
make all test install
in a directory other than the perl source directory.
See INSTALL.
"Configure -S" can be run non-interactively.
Documentation
README.aix, README.solaris and README.macos have been
added. README.posix-bc has been renamed to README.bs2000.
These are installed as the perlaix manpage, the perlso
laris manpage, the perlmacos manpage, and the perlbs2000
manpage respectively.
The following pod documents are brand new:
perlclib Internal replacements for standard C library functions
perldebtut Perl debugging tutorial
perlebcdic Considerations for running Perl on EBCDIC platforms
perlnewmod Perl modules: preparing a new module for distribution
perlrequick Perl regular expressions quick start
perlretut Perl regular expressions tutorial
perlutil utilities packaged with the Perl distribution
The INSTALL file has been expanded to cover various
issues, such as 64-bit support.
A longer list of contributors has been added to the source
distribution. See the file "AUTHORS".
Numerous other changes have been made to the included doc
umentation and FAQs.
Bundled modules
The following modules have been added.
B::Concise
Walks Perl syntax tree, printing concise info about
ops. See the B::Concise manpage.
File::Temp
Returns name and handle of a temporary file safely.
See the File::Temp manpage.
Pod::LaTeX
Converts Pod data to formatted LaTeX. See the
Pod::LaTeX manpage.
Pod::Text::Overstrike
Converts POD data to formatted overstrike text. See
the Pod::Text::Overstrike manpage.
The following modules have been upgraded.
CGI CGI v2.752 is now included.
CPAN
CPAN v1.59_54 is now included.
Class::Struct
Various bugfixes have been added.
DB_File
DB_File v1.75 supports newer Berkeley DB versions,
among other improvements.
Devel::Peek
Devel::Peek has been enhanced to support dumping of
memory statistics, when perl is built with the
included malloc().
File::Find
File::Find now supports pre and post-processing of the
files in order to sort() them, etc.
Getopt::Long
Getopt::Long v2.25 is included.
IO::Poll
Various bug fixes have been included.
IPC::Open3
IPC::Open3 allows use of numeric file descriptors.
Math::BigFloat
The fmod() function supports modulus operations. Var
ious bug fixes have also been included.
Math::Complex
Math::Complex handles inf, NaN etc., better.
Net::Ping
ping() could fail on odd number of data bytes, and
when the echo service isn't running. This has been
corrected.
Opcode
A memory leak has been fixed.
Pod::Parser
Version 1.13 of the Pod::Parser suite is included.
Pod::Text
Pod::Text and related modules have been upgraded to
the versions in podlators suite v2.08.
SDBM_File
On dosish platforms, some keys went missing because of
lack of support for files with "holes". A workaround
for the problem has been added.
Sys::Syslog
Various bug fixes have been included.
Tie::RefHash
Now supports Tie::RefHash::Nestable to automagically
tie hashref values.
Tie::SubstrHash
Various bug fixes have been included.
Platform-specific improvements
The following new ports are now available.
NCR MP-RAS
NonStop-UX
Perl now builds under Amdahl UTS.
Perl has also been verified to build under Amiga OS.
Support for EPOC has been much improved. See README.epoc.
Building perl with -Duseithreads or -Duse5005threads now
works under HP-UX 10.20 (previously it only worked under
10.30 or later). You will need a thread library package
installed. See README.hpux.
Long doubles should now work under Linux.
MacOS Classic is now supported in the mainstream source
package. See README.macos.
Support for MPE/iX has been updated. See README.mpeix.
Support for OS/2 has been improved. See "os2/Changes" and
README.os2.
Dynamic loading on z/OS (formerly OS/390) has been
improved. See README.os390.
Support for VMS has seen many incremental improvements,
including better support for operators like backticks and
system(), and better %ENV handling. See "README.vms" and
the perlvms manpage.
Support for Stratus VOS has been improved. See
"vos/Changes" and README.vos.
Support for Windows has been improved.
fork() emulation has been improved in various ways,
but still continues to be experimental. See the perl
fork manpage for known bugs and caveats.
%SIG has been enabled under USE_ITHREADS, but its use
is completely unsupported under all configurations.
Borland C++ v5.5 is now a supported compiler that can
build Perl. However, the generated binaries continue
to be incompatible with those generated by the other
supported compilers (GCC and Visual C++).
Non-blocking waits for child processes (or pseudo-pro
cesses) are supported via "waitpid($pid, &POSIX::WNO
HANG)".
A memory leak in accept() has been fixed.
wait(), waitpid() and backticks now return the correct
exit status under Windows 9x.
Trailing new %ENV entries weren't propagated to child
processes. This is now fixed.
Current directory entries in %ENV are now correctly
propagated to child processes.
Duping socket handles with open(F, ">&MYSOCK") now
works under Windows 9x.
The makefiles now provide a single switch to bulk-
enable all the features enabled in ActiveState
ActivePerl (a popular binary distribution).
Win32::GetCwd() correctly returns C:\ instead of C:
when at the drive root. Other bugs in chdir() and
Cwd::cwd() have also been fixed.
fork() correctly returns undef and sets EAGAIN when it
runs out of pseudo-process handles.
ExtUtils::MakeMaker now uses $ENV{LIB} to search for
libraries.
UNC path handling is better when perl is built to sup
port fork().
A handle leak in socket handling has been fixed.
send() works from within a pseudo-process.
Unless specifically qualified otherwise, the remainder of
this document covers changes between the 5.005 and 5.6.0
releases.
Core Enhancements
Interpreter cloning, threads, and concurrency
Perl 5.6.0 introduces the beginnings of support for run
ning multiple interpreters concurrently in different
threads. In conjunction with the perl_clone() API call,
which can be used to selectively duplicate the state of
any given interpreter, it is possible to compile a piece
of code once in an interpreter, clone that interpreter one
or more times, and run all the resulting interpreters in
distinct threads.
On the Windows platform, this feature is used to emulate
fork() at the interpreter level. See the perlfork manpage
for details about that.
This feature is still in evolution. It is eventually
meant to be used to selectively clone a subroutine and
data reachable from that subroutine in a separate inter
preter and run the cloned subroutine in a separate thread.
Since there is no shared data between the interpreters,
little or no locking will be needed (unless parts of the
symbol table are explicitly shared). This is obviously
intended to be an easy-to-use replacement for the existing
threads support.
Support for cloning interpreters and interpreter concur
rency can be enabled using the -Dusethreads Configure
option (see win32/Makefile for how to enable it on Win
dows.) The resulting perl executable will be functionally
identical to one that was built with -Dmultiplicity, but
the perl_clone() API call will only be available in the
former.
-Dusethreads enables the cpp macro USE_ITHREADS by
default, which in turn enables Perl source code changes
that provide a clear separation between the op tree and
the data it operates with. The former is immutable, and
can therefore be shared between an interpreter and all of
its clones, while the latter is considered local to each
interpreter, and is therefore copied for each clone.
Note that building Perl with the -Dusemultiplicity Config
ure option is adequate if you wish to run multiple inde
pendent interpreters concurrently in different threads.
-Dusethreads only provides the additional functionality of
the perl_clone() API call and other support for running
cloned interpreters concurrently.
NOTE: This is an experimental feature. Implementation details are
subject to change.
Lexically scoped warning categories
You can now control the granularity of warnings emitted by
perl at a finer level using the "use warnings" pragma.
the warnings manpage and the perllexwarn manpage have
copious documentation on this feature.
Unicode and UTF-8 support
Perl now uses UTF-8 as its internal representation for
character strings. The "utf8" and "bytes" pragmas are
used to control this support in the current lexical scope.
See the perlunicode manpage, the utf8 manpage and the
bytes manpage for more information.
This feature is expected to evolve quickly to support some
form of I/O disciplines that can be used to specify the
kind of input and output data (bytes or characters).
Until that happens, additional modules from CPAN will be
needed to complete the toolkit for dealing with Unicode.
NOTE: This should be considered an experimental feature. Implementation
details are subject to change.
Support for interpolating named characters
The new "\N" escape interpolates named characters within
strings. For example, ""Hi! \N{WHITE SMILING FACE}""
evaluates to a string with a Unicode smiley face at the
end.
"our" declarations
An "our" declaration introduces a value that can be best
understood as a lexically scoped symbolic alias to a
global variable in the package that was current where the
variable was declared. This is mostly useful as an alter
native to the "vars" pragma, but also provides the oppor
tunity to introduce typing and other attributes for such
variables. See the our entry in the perlfunc manpage.
Support for strings represented as a vector of ordinals
Literals of the form "v1.2.3.4" are now parsed as a string
composed of characters with the specified ordinals. This
is an alternative, more readable way to construct
(possibly Unicode) strings instead of interpolating char
acters, as in ""\x{1}\x{2}\x{3}\x{4}"". The leading "v"
may be omitted if there are more than two ordinals, so
"1.2.3" is parsed the same as "v1.2.3".
Strings written in this form are also useful to represent
version "numbers". It is easy to compare such version
"numbers" (which are really just plain strings) using any
of the usual string comparison operators "eq", "ne", "lt",
"gt", etc., or perform bitwise string operations on them
using "|", "&", etc.
In conjunction with the new "$^V" magic variable (which
contains the perl version as a string), such literals can
be used as a readable way to check if you're running a
particular version of Perl:
# this will parse in older versions of Perl also
if ($^V and $^V gt v5.6.0) {
# new features supported
}
"require" and "use" also have some special magic to sup
port such literals. They will be interpreted as a version
rather than as a module name:
require v5.6.0; # croak if $^V lt v5.6.0
use v5.6.0; # same, but croaks at compile-time
Alternatively, the "v" may be omitted if there is more
than one dot:
require 5.6.0;
use 5.6.0;
Also, "sprintf" and "printf" support the Perl-specific
format flag "%v" to print ordinals of characters in arbi
trary strings:
printf "v%vd", $^V; # prints current version, such as "v5.5.650"
printf "%*vX", ":", $addr; # formats IPv6 address
printf "%*vb", " ", $bits; # displays bitstring
See the Scalar value constructors entry in the perldata
manpage for additional information.
Improved Perl version numbering system
Beginning with Perl version 5.6.0, the version number con
vention has been changed to a "dotted integer" scheme that
is more commonly found in open source projects.
Maintenance versions of v5.6.0 will be released as v5.6.1,
v5.6.2 etc. The next development series following v5.6.0
will be numbered v5.7.x, beginning with v5.7.0, and the
next major production release following v5.6.0 will be
v5.8.0.
The English module now sets $PERL_VERSION to $^V (a string
value) rather than "$]" (a numeric value). (This is a
potential incompatibility. Send us a report via perlbug
if you are affected by this.)
The v1.2.3 syntax is also now legal in Perl. See the Sup
port for strings represented as a vector of ordinals entry
elsewhere in this document for more on that.
To cope with the new versioning system's use of at least
three significant digits for each version component, the
method used for incrementing the subversion number has
also changed slightly. We assume that versions older than
v5.6.0 have been incrementing the subversion component in
multiples of 10. Versions after v5.6.0 will increment
them by 1. Thus, using the new notation, 5.005_03 is the
"same" as v5.5.30, and the first maintenance version fol
lowing v5.6.0 will be v5.6.1 (which should be read as
being equivalent to a floating point value of 5.006_001 in
the older format, stored in "$]").
New syntax for declaring subroutine attributes
Formerly, if you wanted to mark a subroutine as being a
method call or as requiring an automatic lock() when it is
entered, you had to declare that with a "use attrs" pragma
in the body of the subroutine. That can now be accom
plished with declaration syntax, like this:
sub mymethod : locked method ;
...
sub mymethod : locked method {
...
}
sub othermethod :locked :method ;
...
sub othermethod :locked :method {
...
}
(Note how only the first ":" is mandatory, and whitespace
surrounding the ":" is optional.)
AutoSplit.pm and SelfLoader.pm have been updated to keep
the attributes with the stubs they provide. See the
attributes manpage.
File and directory handles can be autovivified
Similar to how constructs such as "$x->[0]" autovivify a
reference, handle constructors (open(), opendir(), pipe(),
socketpair(), sysopen(), socket(), and accept()) now auto
vivify a file or directory handle if the handle passed to
them is an uninitialized scalar variable. This allows the
constructs such as "open(my $fh, ...)" and "open(local
$fh,...)" to be used to create filehandles that will con
veniently be closed automatically when the scope ends,
provided there are no other references to them. This
largely eliminates the need for typeglobs when opening
filehandles that must be passed around, as in the follow
ing example:
sub myopen {
open my $fh, "@_"
or die "Can't open '@_': $!";
return $fh;
}
{
my $f = myopen("</etc/motd");
print <$f>;
# $f implicitly closed here
}
open() with more than two arguments
If open() is passed three arguments instead of two, the
second argument is used as the mode and the third argument
is taken to be the file name. This is primarily useful
for protecting against unintended magic behavior of the
traditional two-argument form. See the open entry in the
perlfunc manpage.
64-bit support
Any platform that has 64-bit integers either
(1) natively as longs or ints
(2) via special compiler flags
(3) using long long or int64_t
is able to use "quads" (64-bit integers) as follows:
constants (decimal, hexadecimal, octal, binary) in the
code
arguments to oct() and hex()
arguments to print(), printf() and sprintf() (flag
prefixes ll, L, q)
printed as such
pack() and unpack() "q" and "Q" formats
in basic arithmetics: + - * / % (NOTE: operating close
to the limits of the integer values may produce sur
prising results)
in bit arithmetics: & | ^ ~ << >> (NOTE: these used to
be forced to be 32 bits wide but now operate on the
full native width.)
vec()
Note that unless you have the case (a) you will have to
configure and compile Perl using the -Duse64bitint Config
ure flag.
NOTE: The Configure flags -Duselonglong and -Duse64bits have been
deprecated. Use -Duse64bitint instead.
There are actually two modes of 64-bitness: the first one
is achieved using Configure -Duse64bitint and the second
one using Configure -Duse64bitall. The difference is that
the first one is minimal and the second one maximal. The
first works in more places than the second.
The "use64bitint" does only as much as is required to get
64-bit integers into Perl (this may mean, for example,
using "long longs") while your memory may still be limited
to 2 gigabytes (because your pointers could still be
32-bit). Note that the name "64bitint" does not imply
that your C compiler will be using 64-bit "int"s (it
might, but it doesn't have to): the "use64bitint" means
that you will be able to have 64 bits wide scalar values.
The "use64bitall" goes all the way by attempting to switch
also integers (if it can), longs (and pointers) to being
64-bit. This may create an even more binary incompatible
Perl than -Duse64bitint: the resulting executable may not
run at all in a 32-bit box, or you may have to
reboot/reconfigure/rebuild your operating system to be
64-bit aware.
Natively 64-bit systems like Alpha and Cray need neither
-Duse64bitint nor -Duse64bitall.
Last but not least: note that due to Perl's habit of
always using floating point numbers, the quads are still
not true integers. When quads overflow their limits
(0...18_446_744_073_709_551_615 unsigned,
-9_223_372_036_854_775_808...9_223_372_036_854_775_807
signed), they are silently promoted to floating point num
bers, after which they will start losing precision (in
their lower digits).
NOTE: 64-bit support is still experimental on most platforms.
Existing support only covers the LP64 data model. In particular, the
LLP64 data model is not yet supported. 64-bit libraries and system
APIs on many platforms have not stabilized--your mileage may vary.
Large file support
If you have filesystems that support "large files" (files
larger than 2 gigabytes), you may now also be able to cre
ate and access them from Perl.
NOTE: The default action is to enable large file support, if
available on the platform.
If the large file support is on, and you have a Fcntl con
stant O_LARGEFILE, the O_LARGEFILE is automatically added
to the flags of sysopen().
Beware that unless your filesystem also supports "sparse
files" seeking to umpteen petabytes may be inadvisable.
Note that in addition to requiring a proper file system to
do large files you may also need to adjust your per-pro
cess (or your per-system, or per-process-group, or per-
user-group) maximum filesize limits before running Perl
scripts that try to handle large files, especially if you
intend to write such files.
Finally, in addition to your process/process group maximum
filesize limits, you may have quota limits on your
filesystems that stop you (your user id or your user group
id) from using large files.
Adjusting your process/user/group/file system/operating
system limits is outside the scope of Perl core language.
For process limits, you may try increasing the limits
using your shell's limits/limit/ulimit command before run
ning Perl. The BSD::Resource extension (not included with
the standard Perl distribution) may also be of use, it
offers the getrlimit/setrlimit interface that can be used
to adjust process resource usage limits, including the
maximum filesize limit.
Long doubles
In some systems you may be able to use long doubles to
enhance the range and precision of your double precision
floating point numbers (that is, Perl's numbers). Use
Configure -Duselongdouble to enable this support (if it is
available).
"more bits"
You can "Configure -Dusemorebits" to turn on both the
64-bit support and the long double support.
Enhanced support for sort() subroutines
Perl subroutines with a prototype of "($$)", and XSUBs in
general, can now be used as sort subroutines. In either
case, the two elements to be compared are passed as normal
parameters in @_. See the sort entry in the perlfunc man
page.
For unprototyped sort subroutines, the historical behavior
of passing the elements to be compared as the global vari
ables $a and $b remains unchanged.
"sort $coderef @foo" allowed
sort() did not accept a subroutine reference as the com
parison function in earlier versions. This is now permit
ted.
File globbing implemented internally
Perl now uses the File::Glob implementation of the glob()
operator automatically. This avoids using an external csh
process and the problems associated with it.
NOTE: This is currently an experimental feature. Interfaces and
implementation are subject to change.
Support for CHECK blocks
In addition to "BEGIN", "INIT", "END", "DESTROY" and
"AUTOLOAD", subroutines named "CHECK" are now special.
These are queued up during compilation and behave similar
to END blocks, except they are called at the end of compi
lation rather than at the end of execution. They cannot
be called directly.
POSIX character class syntax [: :] supported
For example to match alphabetic characters use
/[[:alpha:]]/. See the perlre manpage for details.
Better pseudo-random number generator
In 5.005_0x and earlier, perl's rand() function used the C
library rand(3) function. As of 5.005_52, Configure tests
for drand48(), random(), and rand() (in that order) and
picks the first one it finds.
These changes should result in better random numbers from
rand().
Improved "qw//" operator
The "qw//" operator is now evaluated at compile time into
a true list instead of being replaced with a run time call
to "split()". This removes the confusing misbehaviour of
"qw//" in scalar context, which had inherited that
behaviour from split().
Thus:
$foo = ($bar) = qw(a b c); print "$foo|$bar\n";
now correctly prints "3|a", instead of "2|a".
Better worst-case behavior of hashes
Small changes in the hashing algorithm have been imple
mented in order to improve the distribution of lower order
bits in the hashed value. This is expected to yield bet
ter performance on keys that are repeated sequences.
pack() format 'Z' supported
The new format type 'Z' is useful for packing and unpack
ing null-terminated strings. See the pack entry in the
perlfunc manpage.
pack() format modifier '!' supported
The new format type modifier '!' is useful for packing and
unpacking native shorts, ints, and longs. See the pack
entry in the perlfunc manpage.
pack() and unpack() support counted strings
The template character '/' can be used to specify a
counted string type to be packed or unpacked. See the
pack entry in the perlfunc manpage.
Comments in pack() templates
The '#' character in a template introduces a comment up to
end of the line. This facilitates documentation of pack()
templates.
Weak references
In previous versions of Perl, you couldn't cache objects
so as to allow them to be deleted if the last reference
from outside the cache is deleted. The reference in the
cache would hold a reference count on the object and the
objects would never be destroyed.
Another familiar problem is with circular references.
When an object references itself, its reference count
would never go down to zero, and it would not get
destroyed until the program is about to exit.
Weak references solve this by allowing you to "weaken" any
reference, that is, make it not count towards the refer
ence count. When the last non-weak reference to an object
is deleted, the object is destroyed and all the weak ref
erences to the object are automatically undef-ed.
To use this feature, you need the WeakRef package from
CPAN, which contains additional documentation.
NOTE: This is an experimental feature. Details are subject to change.
Binary numbers supported
Binary numbers are now supported as literals, in s?printf
formats, and "oct()":
$answer = 0b101010;
printf "The answer is: %b\n", oct("0b101010");
Lvalue subroutines
Subroutines can now return modifiable lvalues. See the
Lvalue subroutines entry in the perlsub manpage.
NOTE: This is an experimental feature. Details are subject to change.
Some arrows may be omitted in calls through references
Perl now allows the arrow to be omitted in many constructs
involving subroutine calls through references. For exam
ple, "$foo[10]->('foo')" may now be written
"$foo[10]('foo')". This is rather similar to how the
arrow may be omitted from "$foo[10]->{'foo'}". Note how
ever, that the arrow is still required for
"foo(10)->('bar')".
Boolean assignment operators are legal lvalues
Constructs such as "($a ||= 2) += 1" are now allowed.
exists() is supported on subroutine names
The exists() builtin now works on subroutine names. A
subroutine is considered to exist if it has been declared
(even if implicitly). See the exists entry in the perl
func manpage for examples.
exists() and delete() are supported on array elements
The exists() and delete() builtins now work on simple
arrays as well. The behavior is similar to that on hash
elements.
exists() can be used to check whether an array element has
been initialized. This avoids autovivifying array ele
ments that don't exist. If the array is tied, the
EXISTS() method in the corresponding tied package will be
invoked.
delete() may be used to remove an element from the array
and return it. The array element at that position returns
to its uninitialized state, so that testing for the same
element with exists() will return false. If the element
happens to be the one at the end, the size of the array
also shrinks up to the highest element that tests true for
exists(), or 0 if none such is found. If the array is
tied, the DELETE() method in the corresponding tied pack
age will be invoked.
See the exists entry in the perlfunc manpage and the
delete entry in the perlfunc manpage for examples.
Pseudo-hashes work better
Dereferencing some types of reference values in a pseudo-
hash, such as "$ph->{foo}[1]", was accidentally disal
lowed. This has been corrected.
When applied to a pseudo-hash element, exists() now
reports whether the specified value exists, not merely if
the key is valid.
delete() now works on pseudo-hashes. When given a pseudo-
hash element or slice it deletes the values corresponding
to the keys (but not the keys themselves). See the
Pseudo-hashes: Using an array as a hash entry in the perl
ref manpage.
Pseudo-hash slices with constant keys are now optimized to
array lookups at compile-time.
List assignments to pseudo-hash slices are now supported.
The "fields" pragma now provides ways to create pseudo-
hashes, via fields::new() and fields::phash(). See the
fields manpage.
NOTE: The pseudo-hash data type continues to be experimental.
Limiting oneself to the interface elements provided by the
fields pragma will provide protection from any future changes.
Automatic flushing of output buffers
fork(), exec(), system(), qx//, and pipe open()s now flush
buffers of all files opened for output when the operation
was attempted. This mostly eliminates confusing buffering
mishaps suffered by users unaware of how Perl internally
handles I/O.
This is not supported on some platforms like Solaris where
a suitably correct implementation of fflush(NULL) isn't
available.
Better diagnostics on meaningless filehandle operations
Constructs such as "open(<FH>)" and "close(<FH>)" are com
pile time errors. Attempting to read from filehandles
that were opened only for writing will now produce warn
ings (just as writing to read-only filehandles does).
Where possible, buffered data discarded from duped input
filehandle
"open(NEW, "<&OLD")" now attempts to discard any data that
was previously read and buffered in "OLD" before duping
the handle. On platforms where doing this is allowed, the
next read operation on "NEW" will return the same data as
the corresponding operation on "OLD". Formerly, it would
have returned the data from the start of the following
disk block instead.
eof() has the same old magic as <>
"eof()" would return true if no attempt to read from "<>"
had yet been made. "eof()" has been changed to have a
little magic of its own, it now opens the "<>" files.
binmode() can be used to set :crlf and :raw modes
binmode() now accepts a second argument that specifies a
discipline for the handle in question. The two pseudo-
disciplines ":raw" and ":crlf" are currently supported on
DOS-derivative platforms. See the binmode entry in the
perlfunc manpage and the open manpage.
"-T" filetest recognizes UTF-8 encoded files as "text"
The algorithm used for the "-T" filetest has been enhanced
to correctly identify UTF-8 content as "text".
system(), backticks and pipe open now reflect exec() fail
ure
On Unix and similar platforms, system(), qx() and
open(FOO, "cmd |") etc., are implemented via fork() and
exec(). When the underlying exec() fails, earlier ver
sions did not report the error properly, since the exec()
happened to be in a different process.
The child process now communicates with the parent about
the error in launching the external command, which allows
these constructs to return with their usual error value
and set $!.
Improved diagnostics
Line numbers are no longer suppressed (under most likely
circumstances) during the global destruction phase.
Diagnostics emitted from code running in threads other
than the main thread are now accompanied by the thread ID.
Embedded null characters in diagnostics now actually show
up. They used to truncate the message in prior versions.
$foo::a and $foo::b are now exempt from "possible typo"
warnings only if sort() is encountered in package "foo".
Unrecognized alphabetic escapes encountered when parsing
quote constructs now generate a warning, since they may
take on new semantics in later versions of Perl.
Many diagnostics now report the internal operation in
which the warning was provoked, like so:
Use of uninitialized value in concatenation (.) at (eval 1) line 1.
Use of uninitialized value in print at (eval 1) line 1.
Diagnostics that occur within eval may also report the
file and line number where the eval is located, in addi
tion to the eval sequence number and the line number
within the evaluated text itself. For example:
Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
Diagnostics follow STDERR
Diagnostic output now goes to whichever file the "STDERR"
handle is pointing at, instead of always going to the
underlying C runtime library's "stderr".
More consistent close-on-exec behavior
On systems that support a close-on-exec flag on filehan
dles, the flag is now set for any handles created by
pipe(), socketpair(), socket(), and accept(), if that is
warranted by the value of $^F that may be in effect. Ear
lier versions neglected to set the flag for handles cre
ated with these operators. See the pipe entry in the
perlfunc manpage, the socketpair entry in the perlfunc
manpage, the socket entry in the perlfunc manpage, the
accept entry in the perlfunc manpage, and the section on
"$^F" in the perlvar manpage.
syswrite() ease-of-use
The length argument of "syswrite()" has become optional.
Better syntax checks on parenthesized unary operators
Expressions such as:
print defined(&foo,&bar,&baz);
print uc("foo","bar","baz");
undef($foo,&bar);
used to be accidentally allowed in earlier versions, and
produced unpredictable behaviour. Some produced ancillary
warnings when used in this way; others silently did the
wrong thing.
The parenthesized forms of most unary operators that
expect a single argument now ensure that they are not
called with more than one argument, making the cases shown
above syntax errors. The usual behaviour of:
print defined &foo, &bar, &baz;
print uc "foo", "bar", "baz";
undef $foo, &bar;
remains unchanged. See the perlop manpage.
Bit operators support full native integer width
The bit operators (& | ^ ~ << >>) now operate on the full
native integral width (the exact size of which is avail
able in $Config{ivsize}). For example, if your platform
is either natively 64-bit or if Perl has been configured
to use 64-bit integers, these operations apply to 8 bytes
(as opposed to 4 bytes on 32-bit platforms). For porta
bility, be sure to mask off the excess bits in the result
of unary "~", e.g., "~$x & 0xffffffff".
Improved security features
More potentially unsafe operations taint their results for
improved security.
The "passwd" and "shell" fields returned by the getp_
went(), getpwnam(), and getpwuid() are now tainted,
because the user can affect their own encrypted password
and login shell.
The variable modified by shmread(), and messages returned
by msgrcv() (and its object-oriented interface
IPC::SysV::Msg::rcv) are also tainted, because other
untrusted processes can modify messages and shared memory
segments for their own nefarious purposes.
More functional bareword prototype (*)
Bareword prototypes have been rationalized to enable them
to be used to override builtins that accept barewords and
interpret them in a special way, such as "require" or
"do".
Arguments prototyped as "*" will now be visible within the
subroutine as either a simple scalar or as a reference to
a typeglob. See the Prototypes entry in the perlsub man
page.
"require" and "do" may be overridden
"require" and "do 'file'" operations may be overridden
locally by importing subroutines of the same name into the
current package (or globally by importing them into the
CORE::GLOBAL:: namespace). Overriding "require" will also
affect "use", provided the override is visible at compile-
time. See the Overriding Built-in Functions entry in the
perlsub manpage.
$^X variables may now have names longer than one character
Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a
syntax error. Now variable names that begin with a con
trol character may be arbitrarily long. However, for com
patibility reasons, these variables must be written with
explicit braces, as "${^XY}" for example. "${^XYZ}" is
synonymous with ${"\cXYZ"}. Variable names with more than
one control character, such as "${^XY^Z}", are illegal.
The old syntax has not changed. As before, `^X' may be
either a literal control-X character or the two-character
sequence `caret' plus `X'. When braces are omitted, the
variable name stops after the control character. Thus
""$^XYZ"" continues to be synonymous with "$^X . "YZ"" as
before.
As before, lexical variables may not have names beginning
with control characters. As before, variables whose names
begin with a control character are always forced to be in
package `main'. All such variables are reserved for
future extensions, except those that begin with "^_",
which may be used by user programs and are guaranteed not
to acquire special meaning in any future version of Perl.
New variable $^C reflects "-c" switch
"$^C" has a boolean value that reflects whether perl is
being run in compile-only mode (i.e. via the "-c" switch).
Since BEGIN blocks are executed under such conditions,
this variable enables perl code to determine whether
actions that make sense only during normal running are
warranted. See the perlvar manpage.
New variable $^V contains Perl version as a string
"$^V" contains the Perl version number as a string com
posed of characters whose ordinals match the version num
bers, i.e. v5.6.0. This may be used in string compar
isons.
See "Support for strings represented as a vector of ordi
nals" for an example.
Optional Y2K warnings
If Perl is built with the cpp macro "PERL_Y2KWARN"
defined, it emits optional warnings when concatenating the
number 19 with another number.
This behavior must be specifically enabled when running
Configure. See INSTALL and README.Y2K.
Arrays now always interpolate into double-quoted strings
In double-quoted strings, arrays now interpolate, no mat
ter what. The behavior in earlier versions of perl 5 was
that arrays would interpolate into strings if the array
had been mentioned before the string was compiled, and
otherwise Perl would raise a fatal compile-time error. In
versions 5.000 through 5.003, the error was
Literal @example now requires backslash
In versions 5.004_01 through 5.6.0, the error was
In string, @example now must be written as \@example
The idea here was to get people into the habit of writing
""fred\@example.com"" when they wanted a literal "@" sign,
just as they have always written ""Give me back my \$5""
when they wanted a literal "$" sign.
Starting with 5.6.1, when Perl now sees an "@" sign in a
double-quoted string, it always attempts to interpolate an
array, regardless of whether or not the array has been
used or declared already. The fatal error has been down
graded to an optional warning:
Possible unintended interpolation of @example in string
This warns you that ""fred@example.com"" is going to turn
into "fred.com" if you don't backslash the "@". See
http://www.plover.com/~mjd/perl/at-error.html for more
details about the history here.
Modules and Pragmata
Modules
attributes
While used internally by Perl as a pragma, this module
also provides a way to fetch subroutine and variable
attributes. See the attributes manpage.
B The Perl Compiler suite has been extensively reworked
for this release. More of the standard Perl testsuite
passes when run under the Compiler, but there is still
a significant way to go to achieve production quality
compiled executables.
NOTE: The Compiler suite remains highly experimental. The
generated code may not be correct, even when it manages to execute
without errors.
Benchmark
Overall, Benchmark results exhibit lower average error
and better timing accuracy.
You can now run tests for n seconds instead of guess
ing the right number of tests to run: e.g.,
timethese(-5, ...) will run each code for at least 5
CPU seconds. Zero as the "number of repetitions"
means "for at least 3 CPU seconds". The output format
has also changed. For example:
use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
will now output something like this:
Benchmark: running a, b, each for at least 5 CPU seconds...
a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
New features: "each for at least N CPU seconds...",
"wallclock secs", and the "@ operations/CPU second
(n=operations)".
timethese() now returns a reference to a hash of
Benchmark objects containing the test results, keyed
on the names of the tests.
timethis() now returns the iterations field in the
Benchmark result object instead of 0.
timethese(), timethis(), and the new cmpthese() (see
below) can also take a format specifier of 'none' to
suppress output.
A new function countit() is just like timeit() except
that it takes a TIME instead of a COUNT.
A new function cmpthese() prints a chart comparing the
results of each test returned from a timethese() call.
For each possible pair of tests, the percentage speed
difference (iters/sec or seconds/iter) is shown.
For other details, see the Benchmark manpage.
ByteLoader
The ByteLoader is a dedicated extension to generate
and run Perl bytecode. See the ByteLoader manpage.
constant
References can now be used.
The new version also allows a leading underscore in
constant names, but disallows a double leading under
score (as in "__LINE__"). Some other names are disal
lowed or warned against, including BEGIN, END, etc.
Some names which were forced into main:: used to fail
silently in some cases; now they're fatal (outside of
main::) and an optional warning (inside of main::).
The ability to detect whether a constant had been set
with a given name has been added.
See the constant manpage.
charnames
This pragma implements the "\N" string escape. See
the charnames manpage.
Data::Dumper
A "Maxdepth" setting can be specified to avoid ventur
ing too deeply into deep data structures. See the
Data::Dumper manpage.
The XSUB implementation of Dump() is now automatically
called if the "Useqq" setting is not in use.
Dumping "qr//" objects works correctly.
DB "DB" is an experimental module that exposes a clean
abstraction to Perl's debugging API.
DB_File
DB_File can now be built with Berkeley DB versions 1,
2 or 3. See "ext/DB_File/Changes".
Devel::DProf
Devel::DProf, a Perl source code profiler has been
added. See the Devel::DProf manpage and the dprofpp
manpage.
Devel::Peek
The Devel::Peek module provides access to the internal
representation of Perl variables and data. It is a
data debugging tool for the XS programmer.
Dumpvalue
The Dumpvalue module provides screen dumps of Perl
data.
DynaLoader
DynaLoader now supports a dl_unload_file() function on
platforms that support unloading shared objects using
dlclose().
Perl can also optionally arrange to unload all exten
sion shared objects loaded by Perl. To enable this,
build Perl with the Configure option
"-Accflags=-DDL_UNLOAD_ALL_AT_EXIT". (This maybe use
ful if you are using Apache with mod_perl.)
English
$PERL_VERSION now stands for "$^V" (a string value)
rather than for "$]" (a numeric value).
Env Env now supports accessing environment variables like
PATH as array variables.
Fcntl
More Fcntl constants added: F_SETLK64, F_SETLKW64,
O_LARGEFILE for large file (more than 4GB) access
(NOTE: the O_LARGEFILE is automatically added to
sysopen() flags if large file support has been config
ured, as is the default), Free/Net/OpenBSD locking
behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
O_ACCMODE: the combined mask of O_RDONLY, O_WRONLY,
and O_RDWR. The seek()/sysseek() constants SEEK_SET,
SEEK_CUR, and SEEK_END are available via the ":seek"
tag. The chmod()/stat() S_IF* constants and S_IS*
functions are available via the ":mode" tag.
File::Compare
A compare_text() function has been added, which allows
custom comparison functions. See the File::Compare
manpage.
File::Find
File::Find now works correctly when the wanted() func
tion is either autoloaded or is a symbolic reference.
A bug that caused File::Find to lose track of the
working directory when pruning top-level directories
has been fixed.
File::Find now also supports several other options to
control its behavior. It can follow symbolic links if
the "follow" option is specified. Enabling the
"no_chdir" option will make File::Find skip changing
the current directory when walking directories. The
"untaint" flag can be useful when running with taint
checks enabled.
See the File::Find manpage.
File::Glob
This extension implements BSD-style file globbing. By
default, it will also be used for the internal imple
mentation of the glob() operator. See the File::Glob
manpage.
File::Spec
New methods have been added to the File::Spec module:
devnull() returns the name of the null device
(/dev/null on Unix) and tmpdir() the name of the temp
directory (normally /tmp on Unix). There are now also
methods to convert between absolute and relative file
names: abs2rel() and rel2abs(). For compatibility
with operating systems that specify volume names in
file paths, the splitpath(), splitdir(), and catdir()
methods have been added.
File::Spec::Functions
The new File::Spec::Functions modules provides a func
tion interface to the File::Spec module. Allows
shorthand
$fullname = catfile($dir1, $dir2, $file);
instead of
$fullname = File::Spec->catfile($dir1, $dir2, $file);
Getopt::Long
Getopt::Long licensing has changed to allow the Perl
Artistic License as well as the GPL. It used to be GPL
only, which got in the way of non-GPL applications
that wanted to use Getopt::Long.
Getopt::Long encourages the use of Pod::Usage to pro
duce help messages. For example:
use Getopt::Long;
use Pod::Usage;
my $man = 0;
my $help = 0;
GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
pod2usage(1) if $help;
pod2usage(-exitstatus => 0, -verbose => 2) if $man;
__END__
=head1 NAME
sample - Using GetOpt::Long and Pod::Usage
=head1 SYNOPSIS
sample [options] [file ...]
Options:
-help brief help message
-man full documentation
=head1 OPTIONS
=over 8
=item B<-help>
Print a brief help message and exits.
=item B<-man>
Prints the manual page and exits.
=back
=head1 DESCRIPTION
B<This program> will read the given input file(s) and do something
useful with the contents thereof.
=cut
See the Pod::Usage manpage for details.
A bug that prevented the non-option call-back <> from
being specified as the first argument has been fixed.
To specify the characters < and > as option starters,
use ><. Note, however, that changing option starters
is strongly deprecated.
IO write() and syswrite() will now accept a single-argu
ment form of the call, for consistency with Perl's
syswrite().
You can now create a TCP-based IO::Socket::INET with
out forcing a connect attempt. This allows you to
configure its options (like making it non-blocking)
and then call connect() manually.
A bug that prevented the IO:\fIs0:Socket::protocol()
accessor from ever returning the correct value has
been corrected.
IO::Socket::connect now uses non-blocking IO instead
of alarm() to do connect timeouts.
IO::Socket::accept now uses select() instead of
alarm() for doing timeouts.
IO::Socket::INET->new now sets $! correctly on fail
ure. $@ is still set for backwards compatibility.
JPL Java Perl Lingo is now distributed with Perl. See
jpl/README for more information.
lib "use lib" now weeds out any trailing duplicate
entries. "no lib" removes all named entries.
Math::BigInt
The bitwise operations "<<", ">>", "&", "|", and "~"
are now supported on bigints.
Math::Complex
The accessor methods Re, Im, arg, abs, rho, and theta
can now also act as mutators (accessor $z->Re(), muta
tor $z->Re(3)).
The class method "display_format" and the correspond
ing object method "display_format", in addition to
accepting just one argument, now can also accept a
parameter hash. Recognized keys of a parameter hash
are ""style"", which corresponds to the old one param
eter case, and two new parameters: ""format"", which
is a printf()-style format string (defaults usually to
""%.15g"", you can revert to the default by setting
the format string to "undef") used for both parts of a
complex number, and ""polar_pretty_print"" (defaults
to true), which controls whether an attempt is made to
try to recognize small multiples and rationals of pi
(2pi, pi/2) at the argument (angle) of a polar complex
number.
The potentially disruptive change is that in list con
text both methods now return the parameter hash,
instead of only the value of the ""style"" parameter.
Math::Trig
A little bit of radial trigonometry (cylindrical and
spherical), radial coordinate conversions, and the
great circle distance were added.
Pod::Parser, Pod::InputObjects
Pod::Parser is a base class for parsing and selecting
sections of pod documentation from an input stream.
This module takes care of identifying pod paragraphs
and commands in the input and hands off the parsed
paragraphs and commands to user-defined methods which
are free to interpret or translate them as they see
fit.
Pod::InputObjects defines some input objects needed by
Pod::Parser, and for advanced users of Pod::Parser
that need more about a command besides its name and
text.
As of release 5.6.0 of Perl, Pod::Parser is now the
officially sanctioned "base parser code" recommended
for use by all pod2xxx translators. Pod::Text
(pod2text) and Pod::Man (pod2man) have already been
converted to use Pod::Parser and efforts to convert
Pod::HTML (pod2html) are already underway. For any
questions or comments about pod parsing and translat
ing issues and utilities, please use the pod-peo
ple@perl.org mailing list.
For further information, please see the Pod::Parser
manpage and the Pod::InputObjects manpage.
Pod::Checker, podchecker
This utility checks pod files for correct syntax,
according to the perlpod manpage. Obvious errors are
flagged as such, while warnings are printed for mis
takes that can be handled gracefully. The checklist
is not complete yet. See the Pod::Checker manpage.
Pod::ParseUtils, Pod::Find
These modules provide a set of gizmos that are useful
mainly for pod translators. Pod::Find traverses
directory structures and returns found pod files,
along with their canonical names (like
"File::Spec::Unix"). Pod::ParseUtils contains
Pod::List (useful for storing pod list information),
Pod::Hyperlink (for parsing the contents of "L<>"
sequences) and Pod::Cache (for caching information
about pod files, e.g., link nodes).
Pod::Select, podselect
Pod::Select is a subclass of Pod::Parser which pro
vides a function named "podselect()" to filter out
user-specified sections of raw pod documentation from
an input stream. podselect is a script that provides
access to Pod::Select from other scripts to be used as
a filter. See the Pod::Select manpage.
Pod::Usage, pod2usage
Pod::Usage provides the function "pod2usage()" to
print usage messages for a Perl script based on its
embedded pod documentation. The pod2usage() function
is generally useful to all script authors since it
lets them write and maintain a single source (the
pods) for documentation, thus removing the need to
create and maintain redundant usage message text con
sisting of information already in the pods.
There is also a pod2usage script which can be used
from other kinds of scripts to print usage messages
from pods (even for non-Perl scripts with pods embed
ded in comments).
For details and examples, please see the Pod::Usage
manpage.
Pod::Text and Pod::Man
Pod::Text has been rewritten to use Pod::Parser.
While pod2text() is still available for backwards com
patibility, the module now has a new preferred inter
face. See the Pod::Text manpage for the details. The
new Pod::Text module is easily subclassed for tweaks
to the output, and two such subclasses
(Pod::Text::Termcap for man-page-style bold and under
lining using termcap information, and Pod::Text::Color
for markup with ANSI color sequences) are now stan
dard.
pod2man has been turned into a module, Pod::Man, which
also uses Pod::Parser. In the process, several out
standing bugs related to quotes in section headers,
quoting of code escapes, and nested lists have been
fixed. pod2man is now a wrapper script around this
module.
SDBM_File
An EXISTS method has been added to this module (and
sdbm_exists() has been added to the underlying sdbm
library), so one can now call exists on an SDBM_File
tied hash and get the correct result, rather than a
runtime error.
A bug that may have caused data loss when more than
one disk block happens to be read from the database in
a single FETCH() has been fixed.
Sys::Syslog
Sys::Syslog now uses XSUBs to access facilities from
syslog.h so it no longer requires syslog.ph to exist.
Sys::Hostname
Sys::Hostname now uses XSUBs to call the C library's
gethostname() or uname() if they exist.
Term::ANSIColor
Term::ANSIColor is a very simple module to provide
easy and readable access to the ANSI color and high
lighting escape sequences, supported by most ANSI ter
minal emulators. It is now included standard.
Time::Local
The timelocal() and timegm() functions used to
silently return bogus results when the date fell out
side the machine's integer range. They now consis
tently croak() if the date falls in an unsupported
range.
Win32
The error return value in list context has been
changed for all functions that return a list of val
ues. Previously these functions returned a list with
a single element "undef" if an error occurred. Now
these functions return the empty list in these situa
tions. This applies to the following functions:
Win32::FsType
Win32::GetOSVersion
The remaining functions are unchanged and continue to
return "undef" on error even in list context.
The Win32::SetLastError(ERROR) function has been added
as a complement to the Win32::GetLastError() function.
The new Win32::GetFullPathName(FILENAME) returns the
full absolute pathname for FILENAME in scalar context.
In list context it returns a two-element list contain
ing the fully qualified directory name and the file
name. See the Win32 manpage.
XSLoader
The XSLoader extension is a simpler alternative to
DynaLoader. See the XSLoader manpage.
DBM Filters
A new feature called "DBM Filters" has been added to
all the DBM modules--DB_File, GDBM_File, NDBM_File,
ODBM_File, and SDBM_File. DBM Filters add four new
methods to each DBM module:
filter_store_key
filter_store_value
filter_fetch_key
filter_fetch_value
These can be used to filter key-value pairs before the
pairs are written to the database or just after they
are read from the database. See the perldbmfilter
manpage for further information.
Pragmata
"use attrs" is now obsolete, and is only provided for
backward-compatibility. It's been replaced by the "sub :
attributes" syntax. See the Subroutine Attributes entry
in the perlsub manpage and the attributes manpage.
Lexical warnings pragma, "use warnings;", to control
optional warnings. See the perllexwarn manpage.
"use filetest" to control the behaviour of filetests ("-r"
"-w" ...). Currently only one subpragma implemented, "use
filetest 'access';", that uses access(2) or equivalent to
check permissions instead of using stat(2) as usual. This
matters in filesystems where there are ACLs (access con
trol lists): the stat(2) might lie, but access(2) knows
better.
The "open" pragma can be used to specify default disci
plines for handle constructors (e.g. open()) and for qx//.
The two pseudo-disciplines ":raw" and ":crlf" are cur
rently supported on DOS-derivative platforms (i.e. where
binmode is not a no-op). See also the binmode() can be
used to set :crlf and :raw modes entry elsewhere in this
document.
Utility Changes
dprofpp
"dprofpp" is used to display profile data generated using
"Devel::DProf". See the dprofpp manpage.
find2perl
The "find2perl" utility now uses the enhanced features of
the File::Find module. The -depth and -follow options are
supported. Pod documentation is also included in the
script.
h2xs
The "h2xs" tool can now work in conjunction with "C::Scan"
(available from CPAN) to automatically parse real-life
header files. The "-M", "-a", "-k", and "-o" options are
new.
perlcc
"perlcc" now supports the C and Bytecode backends. By
default, it generates output from the simple C backend
rather than the optimized C backend.
Support for non-Unix platforms has been improved.
perldoc
"perldoc" has been reworked to avoid possible security
holes. It will not by default let itself be run as the
superuser, but you may still use the -U switch to try to
make it drop privileges first.
The Perl Debugger
Many bug fixes and enhancements were added to perl5db.pl,
the Perl debugger. The help documentation was rearranged.
New commands include "< ?", "> ?", and "{ ?" to list out
current actions, "man docpage" to run your doc viewer on
some perl docset, and support for quoted options. The
help information was rearranged, and should be viewable
once again if you're using less as your pager. A serious
security hole was plugged--you should immediately remove
all older versions of the Perl debugger as installed in
previous releases, all the way back to perl3, from your
system to avoid being bitten by this.
Improved Documentation
Many of the platform-specific README files are now part of
the perl installation. See the perl manpage for the com
plete list.
perlapi.pod
The official list of public Perl API functions.
perlboot.pod
A tutorial for beginners on object-oriented Perl.
perlcompile.pod
An introduction to using the Perl Compiler suite.
perldbmfilter.pod
A howto document on using the DBM filter facility.
perldebug.pod
All material unrelated to running the Perl debugger,
plus all low-level guts-like details that risked
crushing the casual user of the debugger, have been
relocated from the old manpage to the next entry
below.
perldebguts.pod
This new manpage contains excessively low-level mate
rial not related to the Perl debugger, but slightly
related to debugging Perl itself. It also contains
some arcane internal details of how the debugging pro
cess works that may only be of interest to developers
of Perl debuggers.
perlfork.pod
Notes on the fork() emulation currently available for
the Windows platform.
perlfilter.pod
An introduction to writing Perl source filters.
perlhack.pod
Some guidelines for hacking the Perl source code.
perlintern.pod
A list of internal functions in the Perl source code.
(List is currently empty.)
perllexwarn.pod
Introduction and reference information about lexically
scoped warning categories.
perlnumber.pod
Detailed information about numbers as they are repre
sented in Perl.
perlopentut.pod
A tutorial on using open() effectively.
perlreftut.pod
A tutorial that introduces the essentials of refer
ences.
perltootc.pod
A tutorial on managing class data for object modules.
perltodo.pod
Discussion of the most often wanted features that may
someday be supported in Perl.
perlunicode.pod
An introduction to Unicode support features in Perl.
Performance enhancements
Simple sort() using { $a <=> $b } and the like are opti
mized
Many common sort() operations using a simple inlined block
are now optimized for faster performance.
Optimized assignments to lexical variables
Certain operations in the RHS of assignment statements
have been optimized to directly set the lexical variable
on the LHS, eliminating redundant copying overheads.
Faster subroutine calls
Minor changes in how subroutine calls are handled inter
nally provide marginal improvements in performance.
delete(), each(), values() and hash iteration are faster
The hash values returned by delete(), each(), values() and
hashes in a list context are the actual values in the
hash, instead of copies. This results in significantly
better performance, because it eliminates needless copying
in most situations.
Installation and Configuration Improvements-Dusethreads means something different
The -Dusethreads flag now enables the experimental inter
preter-based thread support by default. To get the flavor
of experimental threads that was in 5.005 instead, you
need to run Configure with "-Dusethreads
-Duse5005threads".
As of v5.6.0, interpreter-threads support is still lacking
a way to create new threads from Perl (i.e., "use Thread;"
will not work with interpreter threads). "use Thread;"
continues to be available when you specify the
-Duse5005threads option to Configure, bugs and all.
NOTE: Support for threads continues to be an experimental feature.
Interfaces and implementation are subject to sudden and drastic changes.
New Configure flags
The following new flags may be enabled on the Configure
command line by running Configure with "-Dflag".
usemultiplicity
usethreads useithreads (new interpreter threads: no Perl API yet)
usethreads use5005threads (threads as they were in 5.005)
use64bitint (equal to now deprecated 'use64bits')
use64bitall
uselongdouble
usemorebits
uselargefiles
usesocks (only SOCKS v5 supported)
Threadedness and 64-bitness now more daring
The Configure options enabling the use of threads and the
use of 64-bitness are now more daring in the sense that
they no more have an explicit list of operating systems of
known threads/64-bit capabilities. In other words: if
your operating system has the necessary APIs and
datatypes, you should be able just to go ahead and use
them, for threads by Configure -Dusethreads, and for 64
bits either explicitly by Configure -Duse64bitint or
implicitly if your system has 64-bit wide datatypes. See
also the section on "64-bit support".
Long Doubles
Some platforms have "long doubles", floating point numbers
of even larger range than ordinary "doubles". To enable
using long doubles for Perl's scalars, use -Duselongdou
ble.
-Dusemorebits
You can enable both -Duse64bitint and -Duselongdouble with
-Dusemorebits. See also the section on "64-bit support".
-Duselargefiles
Some platforms support system APIs that are capable of
handling large files (typically, files larger than two
gigabytes). Perl will try to use these APIs if you ask
for -Duselargefiles.
See the section on "Large file support" for more informa
tion.
installusrbinperl
You can use "Configure -Uinstallusrbinperl" which causes
installperl to skip installing perl also as /usr/bin/perl.
This is useful if you prefer not to modify /usr/bin for
some reason or another but harmful because many scripts
assume to find Perl in /usr/bin/perl.
SOCKS support
You can use "Configure -Dusesocks" which causes Perl to
probe for the SOCKS proxy protocol library (v5, not v4).
For more information on SOCKS, see:
http://www.socks.nec.com/
"-A" flag
You can "post-edit" the Configure variables using the Con
figure "-A" switch. The editing happens immediately after
the platform specific hints files have been processed but
before the actual configuration process starts. Run "Con
figure -h" to find out the full "-A" syntax.
Enhanced Installation Directories
The installation structure has been enriched to improve
the support for maintaining multiple versions of perl, to
provide locations for vendor-supplied modules, scripts,
and manpages, and to ease maintenance of locally-added
modules, scripts, and manpages. See the section on
Installation Directories in the INSTALL file for complete
details. For most users building and installing from
source, the defaults should be fine.
If you previously used "Configure -Dsitelib" or
"-Dsitearch" to set special values for library directo
ries, you might wish to consider using the new "-Dsitepre
fix" setting instead. Also, if you wish to re-use a con
fig.sh file from an earlier version of perl, you should be
sure to check that Configure makes sensible choices for
the new directories. See INSTALL for complete details.
gcc automatically tried if 'cc' does not seem to be work
ing
In many platforms the vendor-supplied 'cc' is too
stripped-down to build Perl (basically, the 'cc' doesn't
do ANSI C). If this seems to be the case and the 'cc'
does not seem to be the GNU C compiler 'gcc', an automatic
attempt is made to find and use 'gcc' instead.
Platform specific changes
Supported platforms
The Mach CThreads (NEXTSTEP, OPENSTEP) are now sup
ported by the Thread extension.
GNU/Hurd is now supported.
Rhapsody/Darwin is now supported.
EPOC is now supported (on Psion 5).
The cygwin port (formerly cygwin32) has been greatly
improved.
DOS
Perl now works with djgpp 2.02 (and 2.03 alpha).
Environment variable names are not converted to upper
case any more.
Incorrect exit codes from backticks have been fixed.
This port continues to use its own builtin globbing
(not File::Glob).
OS390 (OpenEdition MVS)
Support for this EBCDIC platform has not been renewed in
this release. There are difficulties in reconciling
Perl's standardization on UTF-8 as its internal represen
tation for characters with the EBCDIC character set,
because the two are incompatible.
It is unclear whether future versions will renew support
for this platform, but the possibility exists.
VMS
Numerous revisions and extensions to configuration, build,
testing, and installation process to accommodate core
changes and VMS-specific options.
Expand %ENV-handling code to allow runtime mapping to log
ical names, CLI symbols, and CRTL environ array.
Extension of subprocess invocation code to accept file
specs as command "verbs".
Add to Perl command line processing the ability to use
default file types and to recognize Unix-style "2>&1".
Expansion of File::Spec::VMS routines, and integration
into ExtUtils::MM_VMS.
Extension of ExtUtils::MM_VMS to handle complex extensions
more flexibly.
Barewords at start of Unix-syntax paths may be treated as
text rather than only as logical names.
Optional secure translation of several logical names used
internally by Perl.
Miscellaneous bugfixing and porting of new core code to
VMS.
Thanks are gladly extended to the many people who have
contributed VMS patches, testing, and ideas.
Win32
Perl can now emulate fork() internally, using multiple
interpreters running in different concurrent threads.
This support must be enabled at build time. See the perl
fork manpage for detailed information.
When given a pathname that consists only of a drivename,
such as "A:", opendir() and stat() now use the current
working directory for the drive rather than the drive
root.
The builtin XSUB functions in the Win32:: namespace are
documented. See the Win32 manpage.
$^X now contains the full path name of the running exe
cutable.
A Win32::GetLongPathName() function is provided to comple
ment Win32::GetFullPathName() and Win32::GetShortPath_
Name(). See the Win32 manpage.
POSIX:\fIs0:uname() is supported.
system(1,...) now returns true process IDs rather than
process handles. kill() accepts any real process id,
rather than strictly return values from system(1,...).
For better compatibility with Unix, "kill(0, $pid)" can
now be used to test whether a process exists.
The "Shell" module is supported.
Better support for building Perl under command.com in Win
dows 95 has been added.
Scripts are read in binary mode by default to allow
ByteLoader (and the filter mechanism in general) to work
properly. For compatibility, the DATA filehandle will be
set to text mode if a carriage return is detected at the
end of the line containing the __END__ or __DATA__ token;
if not, the DATA filehandle will be left open in binary
mode. Earlier versions always opened the DATA filehandle
in text mode.
The glob() operator is implemented via the "File::Glob"
extension, which supports glob syntax of the C shell.
This increases the flexibility of the glob() operator, but
there may be compatibility issues for programs that relied
on the older globbing syntax. If you want to preserve
compatibility with the older syntax, you might want to run
perl with "-MFile::DosGlob". For details and compatibil
ity information, see the File::Glob manpage.
Significant bug fixes
<HANDLE> on empty files
With "$/" set to "undef", "slurping" an empty file returns
a string of zero length (instead of "undef", as it used
to) the first time the HANDLE is read after "$/" is set to
"undef". Further reads yield "undef".
This means that the following will append "foo" to an
empty file (it used to do nothing):
perl -0777 -pi -e 's/^/foo/' empty_file
The behaviour of:
perl -pi -e 's/^/foo/' empty_file
is unchanged (it continues to leave the file empty).
"eval '...'" improvements
Line numbers (as reflected by caller() and most diagnos
tics) within "eval '...'" were often incorrect where here
documents were involved. This has been corrected.
Lexical lookups for variables appearing in "eval '...'"
within functions that were themselves called within an
"eval '...'" were searching the wrong place for lexicals.
The lexical search now correctly ends at the subroutine's
block boundary.
The use of "return" within "eval {...}" caused $@ not to
be reset correctly when no exception occurred within the
eval. This has been fixed.
Parsing of here documents used to be flawed when they
appeared as the replacement expression in "eval
's/.../.../e'". This has been fixed.
All compilation errors are true errors
Some "errors" encountered at compile time were by neces
sity generated as warnings followed by eventual termina
tion of the program. This enabled more such errors to be
reported in a single run, rather than causing a hard stop
at the first error that was encountered.
The mechanism for reporting such errors has been reimple
mented to queue compile-time errors and report them at the
end of the compilation as true errors rather than as warn
ings. This fixes cases where error messages leaked
through in the form of warnings when code was compiled at
run time using "eval STRING", and also allows such errors
to be reliably trapped using "eval "..."".
Implicitly closed filehandles are safer
Sometimes implicitly closed filehandles (as when they are
localized, and Perl automatically closes them on exiting
the scope) could inadvertently set $? or $!. This has
been corrected.
Behavior of list slices is more consistent
When taking a slice of a literal list (as opposed to a
slice of an array or hash), Perl used to return an empty
list if the result happened to be composed of all undef
values.
The new behavior is to produce an empty list if (and only
if) the original list was empty. Consider the following
example:
@a = (1,undef,undef,2)[2,1,2];
The old behavior would have resulted in @a having no ele
ments. The new behavior ensures it has three undefined
elements.
Note in particular that the behavior of slices of the fol
lowing cases remains unchanged:
@a = ()[1,2];
@a = (getpwent)[7,0];
@a = (anything_returning_empty_list())[2,1,2];
@a = @b[2,1,2];
@a = @c{'a','b','c'};
See the perldata manpage.
"(\$)" prototype and "$foo{a}"
A scalar reference prototype now correctly allows a hash
or array element in that slot.
"goto &sub" and AUTOLOAD
The "goto &sub" construct works correctly when "&sub" hap
pens to be autoloaded.
"-bareword" allowed under "use integer"
The autoquoting of barewords preceded by "-" did not work
in prior versions when the "integer" pragma was enabled.
This has been fixed.
Failures in DESTROY()
When code in a destructor threw an exception, it went
unnoticed in earlier versions of Perl, unless someone hap
pened to be looking in $@ just after the point the
destructor happened to run. Such failures are now visible
as warnings when warnings are enabled.
Locale bugs fixed
printf() and sprintf() previously reset the numeric locale
back to the default "C" locale. This has been fixed.
Numbers formatted according to the local numeric locale
(such as using a decimal comma instead of a decimal dot)
caused "isn't numeric" warnings, even while the operations
accessing those numbers produced correct results. These
warnings have been discontinued.
Memory leaks
The "eval 'return sub {...}'" construct could sometimes
leak memory. This has been fixed.
Operations that aren't filehandle constructors used to
leak memory when used on invalid filehandles. This has
been fixed.
Constructs that modified "@_" could fail to deallocate
values in "@_" and thus leak memory. This has been cor
rected.
Spurious subroutine stubs after failed subroutine calls
Perl could sometimes create empty subroutine stubs when a
subroutine was not found in the package. Such cases
stopped later method lookups from progressing into base
packages. This has been corrected.
Taint failures under "-U"
When running in unsafe mode, taint violations could some
times cause silent failures. This has been fixed.
END blocks and the "-c" switch
Prior versions used to run BEGIN and END blocks when Perl
was run in compile-only mode. Since this is typically not
the expected behavior, END blocks are not executed anymore
when the "-c" switch is used, or if compilation fails.
See the Support for CHECK blocks entry elsewhere in this
document for how to run things when the compile phase
ends.
Potential to leak DATA filehandles
Using the "__DATA__" token creates an implicit filehandle
to the file that contains the token. It is the program's
responsibility to close it when it is done reading from
it.
This caveat is now better explained in the documentation.
See the perldata manpage.
New or Changed Diagnostics
""%s"" variable %s masks earlier declaration in same %s
(W misc) A "my" or "our" variable has been redeclared
in the current scope or statement, effectively elimi
nating all access to the previous instance. This is
almost always a typographical error. Note that the
earlier variable will still exist until the end of the
scope or until all closure referents to it are
destroyed.
""my sub"" not yet implemented
(F) Lexically scoped subroutines are not yet imple
mented. Don't try that yet.
""our"" variable %s redeclared
(W misc) You seem to have already declared the same
global once before in the current lexical scope.
'!' allowed only after types %s
(F) The '!' is allowed in pack() and unpack() only
after certain types. See the pack entry in the perl
func manpage.
/ cannot take a count
(F) You had an unpack template indicating a counted-
length string, but you have also specified an explicit
size for the string. See the pack entry in the perl
func manpage.
/ must be followed by a, A or Z
(F) You had an unpack template indicating a counted-
length string, which must be followed by one of the
letters a, A or Z to indicate what sort of string is
to be unpacked. See the pack entry in the perlfunc
manpage.
/ must be followed by a*, A* or Z*
(F) You had a pack template indicating a counted-
length string, Currently the only things that can have
their length counted are a*, A* or Z*. See the pack
entry in the perlfunc manpage.
/ must follow a numeric type
(F) You had an unpack template that contained a '#',
but this did not follow some numeric unpack specifica
tion. See the pack entry in the perlfunc manpage.
/%s/: Unrecognized escape \\%c passed through
(W regexp) You used a backslash-character combination
which is not recognized by Perl. This combination
appears in an interpolated variable or a "'"-delimited
regular expression. The character was understood lit
erally.
/%s/: Unrecognized escape \\%c in character class passed
through
(W regexp) You used a backslash-character combination
which is not recognized by Perl inside character
classes. The character was understood literally.
/%s/ should probably be written as ""%s""
(W syntax) You have used a pattern where Perl expected
to find a string, as in the first argument to "join".
Perl will treat the true or false result of matching
the pattern against $_ as the string, which is proba
bly not what you had in mind.
%s() called too early to check prototype
(W prototype) You've called a function that has a pro
totype before the parser saw a definition or declara
tion for it, and Perl could not check that the call
conforms to the prototype. You need to either add an
early prototype declaration for the subroutine in
question, or move the subroutine definition ahead of
the call to get proper prototype checking. Alterna
tively, if you are certain that you're calling the
function correctly, you may put an ampersand before
the name to avoid the warning. See the perlsub man
page.
%s argument is not a HASH or ARRAY element
(F) The argument to exists() must be a hash or array
element, such as:
$foo{$bar}
$ref->{"susie"}[12]
%s argument is not a HASH or ARRAY element or slice
(F) The argument to delete() must be either a hash or
array element, such as:
$foo{$bar}
$ref->{"susie"}[12]
or a hash or array slice, such as:
@foo[$bar, $baz, $xyzzy]
@{$ref->[12]}{"susie", "queue"}
%s argument is not a subroutine name
(F) The argument to exists() for "exists &sub" must be
a subroutine name, and not a subroutine call. "exists
&sub()" will generate this error.
%s package attribute may clash with future reserved word:
%s
(W reserved) A lowercase attribute name was used that
had a package-specific handler. That name might have
a meaning to Perl itself some day, even though it
doesn't yet. Perhaps you should use a mixed-case
attribute name, instead. See the attributes manpage.
(in cleanup) %s
(W misc) This prefix usually indicates that a
DESTROY() method raised the indicated exception.
Since destructors are usually called by the system at
arbitrary points during execution, and often a vast
number of times, the warning is issued only once for
any number of failures that would otherwise result in
the same message being repeated.
Failure of user callbacks dispatched using the
"G_KEEPERR" flag could also result in this warning.
See the G_KEEPERR entry in the perlcall manpage.
<> should be quotes
(F) You wrote "require <file>" when you should have
written "require 'file'".
Attempt to join self
(F) You tried to join a thread from within itself,
which is an impossible task. You may be joining the
wrong thread, or you may need to move the join() to
some other thread.
Bad evalled substitution pattern
(F) You've used the /e switch to evaluate the replace
ment for a substitution, but perl found a syntax error
in the code to evaluate, most likely an unexpected
right brace '}'.
Bad realloc() ignored
(S) An internal routine called realloc() on something
that had never been malloc()ed in the first place.
Mandatory, but can be disabled by setting environment
variable "PERL_BADFREE" to 1.
Bareword found in conditional
(W bareword) The compiler found a bareword where it
expected a conditional, which often indicates that an
|| or && was parsed as part of the last argument of
the previous construct, for example:
open FOO || die;
It may also indicate a misspelled constant that has
been interpreted as a bareword:
use constant TYPO => 1;
if (TYOP) { print "foo" }
The "strict" pragma is useful in avoiding such errors.
Binary number > 0b11111111111111111111111111111111 non-
portable
(W portable) The binary number you specified is larger
than 2**32-1 (4294967295) and therefore non-portable
between systems. See the perlport manpage for more on
portability concerns.
Bit vector size > 32 non-portable
(W portable) Using bit vector sizes larger than 32 is
non-portable.
Buffer overflow in prime_env_iter: %s
(W internal) A warning peculiar to VMS. While Perl
was preparing to iterate over %ENV, it encountered a
logical name or symbol definition which was too long,
so it was truncated to the string shown.
Can't check filesystem of script ""%s""
(P) For some reason you can't check the filesystem of
the script for nosuid.
Can't declare class for non-scalar %s in ""%s""
(S) Currently, only scalar variables can declared with
a specific class qualifier in a "my" or "our" declara
tion. The semantics may be extended for other types
of variables in future.
Can't declare %s in ""%s""
(F) Only scalar, array, and hash variables may be
declared as "my" or "our" variables. They must have
ordinary identifiers as names.
Can't ignore signal CHLD, forcing to default
(W signal) Perl has detected that it is being run with
the SIGCHLD signal (sometimes known as SIGCLD) dis
abled. Since disabling this signal will interfere
with proper determination of exit status of child pro
cesses, Perl has reset the signal to its default
value. This situation typically indicates that the
parent program under which Perl may be running (e.g.,
cron) is being very careless.
Can't modify non-lvalue subroutine call
(F) Subroutines meant to be used in lvalue context
should be declared as such, see the Lvalue subroutines
entry in the perlsub manpage.
Can't read CRTL environ
(S) A warning peculiar to VMS. Perl tried to read an
element of %ENV from the CRTL's internal environment
array and discovered the array was missing. You need
to figure out where your CRTL misplaced its environ or
define PERL_ENV_TABLES (see the perlvms manpage) so
that environ is not searched.
Can't remove %s: %s, skipping file
(S) You requested an inplace edit without creating a
backup file. Perl was unable to remove the original
file to replace it with the modified file. The file
was left unmodified.
Can't return %s from lvalue subroutine
(F) Perl detected an attempt to return illegal lvalues
(such as temporary or readonly values) from a subrou
tine used as an lvalue. This is not allowed.
Can't weaken a nonreference
(F) You attempted to weaken something that was not a
reference. Only references can be weakened.
Character class [:%s:] unknown
(F) The class in the character class [: :] syntax is
unknown. See the perlre manpage.
Character class syntax [%s] belongs inside character
classes
(W unsafe) The character class constructs [: :], [=
=], and [. .] go inside character classes, the [] are
part of the construct, for example:
/[012[:alpha:]345]/. Note that [= =] and [. .] are
not currently implemented; they are simply placehold
ers for future extensions.
Constant is not %s reference
(F) A constant value (perhaps declared using the "use
constant" pragma) is being dereferenced, but it
amounts to the wrong type of reference. The message
indicates the type of reference that was expected.
This usually indicates a syntax error in dereferencing
the constant value. See the Constant Functions entry
in the perlsub manpage and the constant manpage.
constant(%s): %s
(F) The parser found inconsistencies either while
attempting to define an overloaded constant, or when
trying to find the character name specified in the
"\N{...}" escape. Perhaps you forgot to load the cor
responding "overload" or "charnames" pragma? See the
charnames manpage and the overload manpage.
CORE::%s is not a keyword
(F) The CORE:: namespace is reserved for Perl key
words.
defined(@array) is deprecated
(D) defined() is not usually useful on arrays because
it checks for an undefined scalar value. If you want
to see if the array is empty, just use "if (@array) {
# not empty }" for example.
defined(%hash) is deprecated
(D) defined() is not usually useful on hashes because
it checks for an undefined scalar value. If you want
to see if the hash is empty, just use "if (%hash) { #
not empty }" for example.
Did not produce a valid header
See Server error.
(Did you mean ""local"" instead of ""our""?)
(W misc) Remember that "our" does not localize the
declared global variable. You have declared it again
in the same lexical scope, which seems superfluous.
Document contains no data
See Server error.
entering effective %s failed
(F) While under the "use filetest" pragma, switching
the real and effective uids or gids failed.
false [] range ""%s"" in regexp
(W regexp) A character class range must start and end
at a literal character, not another character class
like "\d" or "[:alpha:]". The "-" in your false range
is interpreted as a literal "-". Consider quoting the
"-", "\-". See the perlre manpage.
Filehandle %s opened only for output
(W io) You tried to read from a filehandle opened only
for writing. If you intended it to be a read/write
filehandle, you needed to open it with "+<" or "+>" or
"+>>" instead of with "<" or nothing. If you intended
only to read from the file, use "<". See the open
entry in the perlfunc manpage.
flock() on closed filehandle %s
(W closed) The filehandle you're attempting to flock()
got itself closed some time before now. Check your
logic flow. flock() operates on filehandles. Are you
attempting to call flock() on a dirhandle by the same
name?
Global symbol ""%s"" requires explicit package name
(F) You've said "use strict vars", which indicates
that all variables must either be lexically scoped
(using "my"), declared beforehand using "our", or
explicitly qualified to say which package the global
variable is in (using "::").
Hexadecimal number > 0xffffffff non-portable
(W portable) The hexadecimal number you specified is
larger than 2**32-1 (4294967295) and therefore non-
portable between systems. See the perlport manpage
for more on portability concerns.
Ill-formed CRTL environ value ""%s""
(W internal) A warning peculiar to VMS. Perl tried to
read the CRTL's internal environ array, and encoun
tered an element without the "=" delimiter used to
separate keys from values. The element is ignored.
Ill-formed message in prime_env_iter: |%s|
(W internal) A warning peculiar to VMS. Perl tried to
read a logical name or CLI symbol definition when
preparing to iterate over %ENV, and didn't see the
expected delimiter between key and value, so the line
was ignored.
Illegal binary digit %s
(F) You used a digit other than 0 or 1 in a binary
number.
Illegal binary digit %s ignored
(W digit) You may have tried to use a digit other than
0 or 1 in a binary number. Interpretation of the
binary number stopped before the offending digit.
Illegal number of bits in vec
(F) The number of bits in vec() (the third argument)
must be a power of two from 1 to 32 (or 64, if your
platform supports that).
Integer overflow in %s number
(W overflow) The hexadecimal, octal or binary number
you have specified either as a literal or as an argu
ment to hex() or oct() is too big for your architec
ture, and has been converted to a floating point num
ber. On a 32-bit architecture the largest hexadeci
mal, octal or binary number representable without
overflow is 0xFFFFFFFF, 037777777777, or
0b11111111111111111111111111111111 respectively. Note
that Perl transparently promotes all numbers to a
floating point representation internally--subject to
loss of precision errors in subsequent operations.
Invalid %s attribute: %s
The indicated attribute for a subroutine or variable
was not recognized by Perl or by a user-supplied han
dler. See the attributes manpage.
Invalid %s attributes: %s
The indicated attributes for a subroutine or variable
were not recognized by Perl or by a user-supplied
handler. See the attributes manpage.
invalid [] range ""%s"" in regexp
The offending range is now explicitly displayed.
Invalid separator character %s in attribute list
(F) Something other than a colon or whitespace was
seen between the elements of an attribute list. If
the previous attribute had a parenthesised parameter
list, perhaps that list was terminated too soon. See
the attributes manpage.
Invalid separator character %s in subroutine attribute
list
(F) Something other than a colon or whitespace was
seen between the elements of a subroutine attribute
list. If the previous attribute had a parenthesised
parameter list, perhaps that list was terminated too
soon.
leaving effective %s failed
(F) While under the "use filetest" pragma, switching
the real and effective uids or gids failed.
Lvalue subs returning %s not implemented yet
(F) Due to limitations in the current implementation,
array and hash values cannot be returned in subrou
tines used in lvalue context. See the Lvalue subrou
tines entry in the perlsub manpage.
Method %s not permitted
See Server error.
Missing %sbrace%s on \N{}
(F) Wrong syntax of character name literal "\N{char
name}" within double-quotish context.
Missing command in piped open
(W pipe) You used the "open(FH, "| command")" or
"open(FH, "command |")" construction, but the command
was missing or blank.
Missing name in ""my sub""
(F) The reserved syntax for lexically scoped subrou
tines requires that they have a name with which they
can be found.
No %s specified for -%c
(F) The indicated command line switch needs a manda
tory argument, but you haven't specified one.
No package name allowed for variable %s in ""our""
(F) Fully qualified variable names are not allowed in
"our" declarations, because that doesn't make much
sense under existing semantics. Such syntax is
reserved for future extensions.
No space allowed after -%c
(F) The argument to the indicated command line switch
must follow immediately after the switch, without
intervening spaces.
no UTC offset information; assuming local time is UTC
(S) A warning peculiar to VMS. Perl was unable to
find the local timezone offset, so it's assuming that
local system time is equivalent to UTC. If it's not,
define the logical name SYS$TIMEZONE_DIFFERENTIAL to
translate to the number of seconds which need to be
added to UTC to get local time.
Octal number > 037777777777 non-portable
(W portable) The octal number you specified is larger
than 2**32-1 (4294967295) and therefore non-portable
between systems. See the perlport manpage for more on
portability concerns.
See also the perlport manpage for writing portable
code.
panic: del_backref
(P) Failed an internal consistency check while trying
to reset a weak reference.
panic: kid popen errno read
(F) forked child returned an incomprehensible message
about its errno.
panic: magic_killbackrefs
(P) Failed an internal consistency check while trying
to reset all weak references to an object.
Parentheses missing around ""%s"" list
(W parenthesis) You said something like
my $foo, $bar = @_;
when you meant
my ($foo, $bar) = @_;
Remember that "my", "our", and "local" bind tighter
than comma.
Possible unintended interpolation of %s in string
(W ambiguous) It used to be that Perl would try to
guess whether you wanted an array interpolated or a
literal @. It no longer does this; arrays are now
always interpolated into strings. This means that if
you try something like:
print "fred@example.com";
and the array "@example" doesn't exist, Perl is going
to print "fred.com", which is probably not what you
wanted. To get a literal "@" sign in a string, put a
backslash before it, just as you would to get a lit
eral "$" sign.
Possible Y2K bug: %s
(W y2k) You are concatenating the number 19 with
another number, which could be a potential Year 2000
problem.
pragma ""attrs"" is deprecated, use ""sub NAME : ATTRS""
instead
(W deprecated) You have written something like this:
sub doit
{
use attrs qw(locked);
}
You should use the new declaration syntax instead.
sub doit : locked
{
...
The "use attrs" pragma is now obsolete, and is only
provided for backward-compatibility. See the Subrou
tine Attributes entry in the perlsub manpage.
Premature end of script headers
See Server error.
Repeat count in pack overflows
(F) You can't specify a repeat count so large that it
overflows your signed integers. See the pack entry in
the perlfunc manpage.
Repeat count in unpack overflows
(F) You can't specify a repeat count so large that it
overflows your signed integers. See the unpack entry
in the perlfunc manpage.
realloc() of freed memory ignored
(S) An internal routine called realloc() on something
that had already been freed.
Reference is already weak
(W misc) You have attempted to weaken a reference that
is already weak. Doing so has no effect.
setpgrp can't take arguments
(F) Your system has the setpgrp() from BSD 4.2, which
takes no arguments, unlike POSIX setpgid(), which
takes a process ID and process group ID.
Strange *+?{} on zero-length expression
(W regexp) You applied a regular expression quantifier
in a place where it makes no sense, such as on a zero-
width assertion. Try putting the quantifier inside
the assertion instead. For example, the way to match
"abc" provided that it is followed by three repeti
tions of "xyz" is "/abc(?=(?:xyz){3})/", not
"/abc(?=xyz){3}/".
switching effective %s is not implemented
(F) While under the "use filetest" pragma, we cannot
switch the real and effective uids or gids.
This Perl can't reset CRTL environ elements (%s)
This Perl can't set CRTL environ elements (%s=%s)
(W internal) Warnings peculiar to VMS. You tried to
change or delete an element of the CRTL's internal
environ array, but your copy of Perl wasn't built with
a CRTL that contained the setenv() function. You'll
need to rebuild Perl with a CRTL that does, or rede
fine PERL_ENV_TABLES (see the perlvms manpage) so that
the environ array isn't the target of the change to
%ENV which produced the warning.
Too late to run %s block
(W void) A CHECK or INIT block is being defined during
run time proper, when the opportunity to run them has
already passed. Perhaps you are loading a file with
"require" or "do" when you should be using "use"
instead. Or perhaps you should put the "require" or
"do" inside a BEGIN block.
Unknown open() mode '%s'
(F) The second argument of 3-argument open() is not
among the list of valid modes: "<", ">", ">>", "+<",
"+>", "+>>", "-|", "|-".
Unknown process %x sent message to prime_env_iter: %s
(P) An error peculiar to VMS. Perl was reading values
for %ENV before iterating over it, and someone else
stuck a message in the stream of data Perl expected.
Someone's very confused, or perhaps trying to subvert
Perl's population of %ENV for nefarious purposes.
Unrecognized escape \\%c passed through
(W misc) You used a backslash-character combination
which is not recognized by Perl. The character was
understood literally.
Unterminated attribute parameter in attribute list
(F) The lexer saw an opening (left) parenthesis char
acter while parsing an attribute list, but the match
ing closing (right) parenthesis character was not
found. You may need to add (or remove) a backslash
character to get your parentheses to balance. See the
attributes manpage.
Unterminated attribute list
(F) The lexer found something other than a simple
identifier at the start of an attribute, and it wasn't
a semicolon or the start of a block. Perhaps you ter
minated the parameter list of the previous attribute
too soon. See the attributes manpage.
Unterminated attribute parameter in subroutine attribute
list
(F) The lexer saw an opening (left) parenthesis char
acter while parsing a subroutine attribute list, but
the matching closing (right) parenthesis character was
not found. You may need to add (or remove) a back
slash character to get your parentheses to balance.
Unterminated subroutine attribute list
(F) The lexer found something other than a simple
identifier at the start of a subroutine attribute, and
it wasn't a semicolon or the start of a block. Per
haps you terminated the parameter list of the previous
attribute too soon.
Value of CLI symbol ""%s"" too long
(W misc) A warning peculiar to VMS. Perl tried to
read the value of an %ENV element from a CLI symbol
table, and found a resultant string longer than 1024
characters. The return value has been truncated to
1024 characters.
Version number must be a constant number
(P) The attempt to translate a "use Module n.n LIST"
statement into its equivalent "BEGIN" block found an
internal inconsistency with the version number.
New tests
lib/attrs
Compatibility tests for "sub : attrs" vs the older
"use attrs".
lib/env
Tests for new environment scalar capability (e.g.,
"use Env qw($BAR);").
lib/env-array
Tests for new environment array capability (e.g., "use
Env qw(@PATH);").
lib/io_const
IO constants (SEEK_*, _IO*).
lib/io_dir
Directory-related IO methods (new, read, close,
rewind, tied delete).
lib/io_multihomed
INET sockets with multi-homed hosts.
lib/io_poll
IO poll().
lib/io_unix
UNIX sockets.
op/attrs
Regression tests for "my ($x,@y,%z) : attrs" and <sub
: attrs>.
op/filetest
File test operators.
op/lex_assign
Verify operations that access pad objects (lexicals
and temporaries).
op/exists_sub
Verify "exists &sub" operations.
Incompatible Changes
Perl Source Incompatibilities
Beware that any new warnings that have been added or old
ones that have been enhanced are not considered incompati
ble changes.
Since all new warnings must be explicitly requested via
the "-w" switch or the "warnings" pragma, it is ultimately
the programmer's responsibility to ensure that warnings
are enabled judiciously.
CHECK is a new keyword
All subroutine definitions named CHECK are now spe
cial. See "/"Support for CHECK blocks"" for more
information.
Treatment of list slices of undef has changed
There is a potential incompatibility in the behavior
of list slices that are comprised entirely of unde
fined values. See the Behavior of list slices is more
consistent entry elsewhere in this document.
Format of $English::PERL_VERSION is different
The English module now sets $PERL_VERSION to $^V (a
string value) rather than "$]" (a numeric value).
This is a potential incompatibility. Send us a report
via perlbug if you are affected by this.
See the Improved Perl version numbering system entry
elsewhere in this document for the reasons for this
change.
Literals of the form ""1.2.3"" parse differently
Previously, numeric literals with more than one dot in
them were interpreted as a floating point number con
catenated with one or more numbers. Such "numbers"
are now parsed as strings composed of the specified
ordinals.
For example, "print 97.98.99" used to output "97.9899"
in earlier versions, but now prints "abc".
See the Support for strings represented as a vector of
ordinals entry elsewhere in this document.
Possibly changed pseudo-random number generator
Perl programs that depend on reproducing a specific
set of pseudo-random numbers may now produce different
output due to improvements made to the rand() builtin.
You can use "sh Configure -Drandfunc=rand" to obtain
the old behavior.
See the Better pseudo-random number generator entry
elsewhere in this document.
Hashing function for hash keys has changed
Even though Perl hashes are not order preserving, the
apparently random order encountered when iterating on
the contents of a hash is actually determined by the
hashing algorithm used. Improvements in the algorithm
may yield a random order that is different from that
of previous versions, especially when iterating on
hashes.
See the Better worst-case behavior of hashes entry
elsewhere in this document for additional information.
""undef"" fails on read only values
Using the "undef" operator on a readonly value (such
as $1) has the same effect as assigning "undef" to the
readonly value--it throws an exception.
Close-on-exec bit may be set on pipe and socket handles
Pipe and socket handles are also now subject to the
close-on-exec behavior determined by the special vari
able $^F.
See the More consistent close-on-exec behavior entry
elsewhere in this document.
Writing """"$$1"""" to mean """"${$}1"""" is unsupported
Perl 5.004 deprecated the interpretation of "$$1" and
similar within interpolated strings to mean "$$ .
"1"", but still allowed it.
In Perl 5.6.0 and later, ""$$1"" always means
""${$1}"".
delete(), each(), values() and ""\(%h)""
operate on aliases to values, not copies
delete(), each(), values() and hashes (e.g. "\(%h)")
in a list context return the actual values in the
hash, instead of copies (as they used to in earlier
versions). Typical idioms for using these constructs
copy the returned values, but this can make a signifi
cant difference when creating references to the
returned values. Keys in the hash are still returned
as copies when iterating on a hash.
See also the delete(), each(), values() and hash iter
ation are faster entry elsewhere in this document.
vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
vec() generates a run-time error if the BITS argument
is not a valid power-of-two integer.
Text of some diagnostic output has changed
Most references to internal Perl operations in diag
nostics have been changed to be more descriptive.
This may be an issue for programs that may incorrectly
rely on the exact text of diagnostics for proper func
tioning.
""%@"" has been removed
The undocumented special variable "%@" that used to
accumulate "background" errors (such as those that
happen in DESTROY()) has been removed, because it
could potentially result in memory leaks.
Parenthesized not() behaves like a list operator
The "not" operator now falls under the "if it looks
like a function, it behaves like a function" rule.
As a result, the parenthesized form can be used with
"grep" and "map". The following construct used to be
a syntax error before, but it works as expected now:
grep not($_), @things;
On the other hand, using "not" with a literal list
slice may not work. The following previously allowed
construct:
print not (1,2,3)[0];
needs to be written with additional parentheses now:
print not((1,2,3)[0]);
The behavior remains unaffected when "not" is not fol
lowed by parentheses.
Semantics of bareword prototype ""(*)"" have changed
The semantics of the bareword prototype "*" have
changed. Perl 5.005 always coerced simple scalar
arguments to a typeglob, which wasn't useful in situa
tions where the subroutine must distinguish between a
simple scalar and a typeglob. The new behavior is to
not coerce bareword arguments to a typeglob. The
value will always be visible as either a simple scalar
or as a reference to a typeglob.
See the More functional bareword prototype (*) entry
elsewhere in this document.
Semantics of bit operators may have changed on 64-bit
platforms
If your platform is either natively 64-bit or if Perl
has been configured to used 64-bit integers, i.e.,
$Config{ivsize} is 8, there may be a potential incom
patibility in the behavior of bitwise numeric opera
tors (& | ^ ~ << >>). These operators used to
strictly operate on the lower 32 bits of integers in
previous versions, but now operate over the entire
native integral width. In particular, note that unary
"~" will produce different results on platforms that
have different $Config{ivsize}. For portability, be
sure to mask off the excess bits in the result of
unary "~", e.g., "~$x & 0xffffffff".
See the Bit operators support full native integer
width entry elsewhere in this document.
More builtins taint their results
As described in the Improved security features entry
elsewhere in this document, there may be more sources
of taint in a Perl program.
To avoid these new tainting behaviors, you can build
Perl with the Configure option "-Accflags=-DINCOM
PLETE_TAINTS". Beware that the ensuing perl binary
may be insecure.
C Source Incompatibilities
""PERL_POLLUTE""
Release 5.005 grandfathered old global symbol names by
providing preprocessor macros for extension source
compatibility. As of release 5.6.0, these preproces
sor definitions are not available by default. You
need to explicitly compile perl with "-DPERL_POLLUTE"
to get these definitions. For extensions still using
the old symbols, this option can be specified via
MakeMaker:
perl Makefile.PL POLLUTE=1
""PERL_IMPLICIT_CONTEXT""
This new build option provides a set of macros for all
API functions such that an implicit interpreter/thread
context argument is passed to every API function. As
a result of this, something like "sv_setsv(foo,bar)"
amounts to a macro invocation that actually translates
to something like "Perl_sv_setsv(my_perl,foo,bar)".
While this is generally expected to not have any sig
nificant source compatibility issues, the difference
between a macro and a real function call will need to
be considered.
This means that there is a source compatibility issue
as a result of this if your extensions attempt to use
pointers to any of the Perl API functions.
Note that the above issue is not relevant to the
default build of Perl, whose interfaces continue to
match those of prior versions (but subject to the
other options described here).
See the The Perl API entry in the perlguts manpage for
detailed information on the ramifications of building
Perl with this option.
NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
with one of -Dusethreads, -Dusemultiplicity, or both. It is not
intended to be enabled by users at this time.
""PERL_POLLUTE_MALLOC""
Enabling Perl's malloc in release 5.005 and earlier
caused the namespace of the system's malloc family of
functions to be usurped by the Perl versions, since by
default they used the same names. Besides causing
problems on platforms that do not allow these func
tions to be cleanly replaced, this also meant that the
system versions could not be called in programs that
used Perl's malloc. Previous versions of Perl have
allowed this behaviour to be suppressed with the HIDE
MYMALLOC and EMBEDMYMALLOC preprocessor definitions.
As of release 5.6.0, Perl's malloc family of functions
have default names distinct from the system versions.
You need to explicitly compile perl with "-DPERL_POL
LUTE_MALLOC" to get the older behaviour. HIDEMYMALLOC
and EMBEDMYMALLOC have no effect, since the behaviour
they enabled is now the default.
Note that these functions do not constitute Perl's
memory allocation API. See the Memory Allocation
entry in the perlguts manpage for further information
about that.
Compatible C Source API Changes
""PATCHLEVEL"" is now ""PERL_VERSION""
The cpp macros "PERL_REVISION", "PERL_VERSION", and
"PERL_SUBVERSION" are now available by default from
perl.h, and reflect the base revision, patchlevel, and
subversion respectively. "PERL_REVISION" had no prior
equivalent, while "PERL_VERSION" and "PERL_SUBVERSION"
were previously available as "PATCHLEVEL" and "SUBVER
SION".
The new names cause less pollution of the cpp names
pace and reflect what the numbers have come to stand
for in common practice. For compatibility, the old
names are still supported when patchlevel.h is explic
itly included (as required before), so there is no
source incompatibility from the change.
Binary Incompatibilities
In general, the default build of this release is expected
to be binary compatible for extensions built with the
5.005 release or its maintenance versions. However, spe
cific platforms may have broken binary compatibility due
to changes in the defaults used in hints files. There
fore, please be sure to always check the platform-specific
README files for any notes to the contrary.
The usethreads or usemultiplicity builds are not binary
compatible with the corresponding builds in 5.005.
On platforms that require an explicit list of exports
(AIX, OS/2 and Windows, among others), purely internal
symbols such as parser functions and the run time opcodes
are not exported by default. Perl 5.005 used to export
all functions irrespective of whether they were considered
part of the public API or not.
For the full list of public API functions, see the perlapi
manpage.
Known Problems
Localizing a tied hash element may leak memory
As of the 5.6.1 release, there is a known leak when code
such as this is executed:
use Tie::Hash;
tie my %tie_hash => 'Tie::StdHash';
...
local($tie_hash{Foo}) = 1; # leaks
Known test failures
64-bit builds
Subtest #15 of lib/b.t may fail under 64-bit builds on
platforms such as HP-UX PA64 and Linux IA64. The
issue is still being investigated.
The lib/io_multihomed test may hang in HP-UX if Perl
has been configured to be 64-bit. Because other
64-bit platforms do not hang in this test, HP-UX is
suspect. All other tests pass in 64-bit HP-UX. The
test attempts to create and connect to "multihomed"
sockets (sockets which have multiple IP addresses).
Note that 64-bit support is still experimental.
Failure of Thread tests
The subtests 19 and 20 of lib/thr5005.t test are known
to fail due to fundamental problems in the 5.005
threading implementation. These are not new fail
ures--Perl 5.005_0x has the same bugs, but didn't have
these tests. (Note that support for 5.005-style
threading remains experimental.)
NEXTSTEP 3.3 POSIX test failure
In NEXTSTEP 3.3p2 the implementation of the strf_
time(3) in the operating system libraries is buggy:
the %j format numbers the days of a month starting
from zero, which, while being logical to programmers,
will cause the subtests 19 to 27 of the lib/posix test
may fail.
Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test
failure with gcc
If compiled with gcc 2.95 the lib/sdbm test will fail
(dump core). The cure is to use the vendor cc, it
comes with the operating system and produces good
code.
EBCDIC platforms not fully supported
In earlier releases of Perl, EBCDIC environments like
OS390 (also known as Open Edition MVS) and VM-ESA were
supported. Due to changes required by the UTF-8 (Unicode)
support, the EBCDIC platforms are not supported in Perl
5.6.0.
The 5.6.1 release improves support for EBCDIC platforms,
but they are not fully supported yet.
UNICOS/mk CC failures during Configure run
In UNICOS/mk the following errors may appear during the
Configure run:
Guessing which symbols your C compiler and preprocessor define...
CC-20 cc: ERROR File = try.c, Line = 3
...
bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
...
4 errors detected in the compilation of "try.c".
The culprit is the broken awk of UNICOS/mk. The effect is
fortunately rather mild: Perl itself is not adversely
affected by the error, only the h2ph utility coming with
Perl, and that is rather rarely needed these days.
Arrow operator and arrays
When the left argument to the arrow operator "->" is an
array, or the "scalar" operator operating on an array, the
result of the operation must be considered erroneous. For
example:
@x->[2]
scalar(@x)->[2]
These expressions will get run-time errors in some future
release of Perl.
Experimental features
As discussed above, many features are still experimental.
Interfaces and implementation of these features are sub
ject to change, and in extreme cases, even subject to
removal in some future release of Perl. These features
include the following:
Threads
Unicode
64-bit support
Lvalue subroutines
Weak references
The pseudo-hash data type
The Compiler suite
Internal implementation of file globbing
The DB module
The regular expression code constructs:
"(?{ code })" and "(??{ code })"
Obsolete Diagnostics
Character class syntax [: :] is reserved for future exten
sions
(W) Within regular expression character classes ([])
the syntax beginning with "[:" and ending with ":]" is
reserved for future extensions. If you need to repre
sent those character sequences inside a regular
expression character class, just quote the square
brackets with the backslash: "\[:" and ":\]".
Ill-formed logical name |%s| in prime_env_iter
(W) A warning peculiar to VMS. A logical name was
encountered when preparing to iterate over %ENV which
violates the syntactic rules governing logical names.
Because it cannot be translated normally, it is
skipped, and will not appear in %ENV. This may be a
benign occurrence, as some software packages might
directly modify logical name tables and introduce non
standard names, or it may indicate that a logical name
table has been corrupted.
In string, @%s now must be written as \@%s
The description of this error used to say:
(Someday it will simply assume that an unbackslashed @
interpolates an array.)
That day has come, and this fatal error has been
removed. It has been replaced by a non-fatal warning
instead. See the Arrays now always interpolate into
double-quoted strings entry elsewhere in this document
for details.
Probable precedence problem on %s
(W) The compiler found a bareword where it expected a
conditional, which often indicates that an || or &&
was parsed as part of the last argument of the previ
ous construct, for example:
open FOO || die;
regexp too big
(F) The current implementation of regular expressions
uses shorts as address offsets within a string.
Unfortunately this means that if the regular expres
sion compiles to longer than 32767, it'll blow up.
Usually when you want a regular expression this big,
there is a better way to do it with multiple state
ments. See the perlre manpage.
Use of ""$$<digit>"" to mean ""${$}<digit>"" is deprecated
(D) Perl versions before 5.004 misinterpreted any type
marker followed by "$" and a digit. For example,
"$$0" was incorrectly taken to mean "${$}0" instead of
"${$0}". This bug is (mostly) fixed in Perl 5.004.
However, the developers of Perl 5.004 could not fix
this bug completely, because at least two widely-used
modules depend on the old meaning of "$$0" in a
string. So Perl 5.004 still interprets "$$<digit>" in
the old (broken) way inside strings; but it generates
this message as a warning. And in Perl 5.005, this
special treatment will cease.
Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc news
group. There may also be information at
http://www.perl.com/, the Perl Home Page.
If you believe you have an unreported bug, please run the
perlbug program included with your release. Be sure to
trim your bug down to a tiny but sufficient test case.
Your bug report, along with the output of "perl -V", will
be sent off to perlbug@perl.org to be analysed by the Perl
porting team.
SEE ALSO
The Changes file for exhaustive details on what changed.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.
HISTORY
Written by Gurusamy Sarathy <gsar@ActiveState.com>, with
many contributions from The Perl Porters.
Send omissions or corrections to <perlbug@perl.org>.
2001-04-07 perl v5.6.1 PERLDELTA(1)
