strict(3) Perl Programmers Reference Guide strict(3)NAMEstrict - Perl pragma to restrict unsafe constructs
SYNOPSIS
use strict;
use strict "vars";
use strict "refs";
use strict "subs";
use strict;
no strict "vars";
DESCRIPTION
If no import list is supplied, all possible restrictions
are assumed. (This is the safest mode to operate in, but
is sometimes too strict for casual programming.) Cur
rently, there are three possible things to be strict
about: "subs", "vars", and "refs".
""strict refs""
This generates a runtime error if you use symbolic
references (see the perlref manpage).
use strict 'refs';
$ref = \$foo;
print $$ref; # ok
$ref = "foo";
print $$ref; # runtime error; normally ok
$file = "STDOUT";
print $file "Hi!"; # error; note: no comma after $file
There is one exception to this rule:
$bar = \&{'foo'};
&$bar;
is allowed so that "goto &$AUTOLOAD" would not break
under stricture.
""strict vars""
This generates a compile-time error if you access a
variable that wasn't declared via "our" or "use
vars", localized via "my()", or wasn't fully quali
fied. Because this is to avoid variable suicide
problems and subtle dynamic scoping issues, a merely
local() variable isn't good enough. See the my
entry in the perlfunc manpage and the local entry in
the perlfunc manpage.
use strict 'vars';
$X::foo = 1; # ok, fully qualified
my $foo = 10; # ok, my() var
local $foo = 9; # blows up
package Cinna;
our $bar; # Declares $bar in current package
$bar = 'HgS'; # ok, global declared via pragma
The local() generated a compile-time error because
you just touched a global name without fully
qualifying it.
Because of their special use by sort(), the vari
ables $a and $b are exempted from this check.
""strict subs""
This disables the poetry optimization, generating a
compile-time error if you try to use a bareword
identifier that's not a subroutine, unless it
appears in curly braces or on the left hand side of
the "=>" symbol.
use strict 'subs';
$SIG{PIPE} = Plumber; # blows up
$SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok
$SIG{PIPE} = \&Plumber; # preferred form
See the Pragmatic Modules entry in the perlmodlib manpage.
2001-02-22 perl v5.6.1 strict(3)
