PERLPOD(1) Perl Programmers Reference Guide PERLPOD(1)NAMEperlpod - plain old documentation
DESCRIPTION
A pod-to-whatever translator reads a pod file paragraph by
paragraph, and translates it to the appropriate output
format. There are three kinds of paragraphs: verbatim,
command, and ordinary text.
Verbatim Paragraph
A verbatim paragraph, distinguished by being indented
(that is, it starts with space or tab). It should be
reproduced exactly, with tabs assumed to be on 8-column
boundaries. There are no special formatting escapes, so
you can't italicize or anything like that. A \ means \,
and nothing else.
Command Paragraph
All command paragraphs start with "=", followed by an
identifier, followed by arbitrary text that the command
can use however it pleases. Currently recognized commands
are
=head1 heading
=head2 heading
=item text
=over N
=back
=cut
=pod
=for X
=begin X
=end X
=pod
=cut
The "=pod" directive does nothing beyond telling the
compiler to lay off parsing code through the next
"=cut". It's useful for adding another paragraph to
the doc if you're mixing up code and pod a lot.
=head1
=head2
Head1 and head2 produce first and second level head
ings, with the text in the same paragraph as the
"=headn" directive forming the heading description.
=over
=back
=item
Item, over, and back require a little more explana
tion: "=over" starts a section specifically for the
generation of a list using "=item" commands. At the
end of your list, use "=back" to end it. You will
probably want to give "4" as the number to "=over", as
some formatters will use this for indentation. The
unit of indentation is optional. If the unit is not
given the natural indentation of the formatting system
applied will be used. Note also that there are some
basic rules to using =item: don't use them outside of
an =over/=back block, use at least one inside an
=over/=back block, you don't _have_ to include the
=back if the list just runs off the document, and per
haps most importantly, keep the items consistent:
either use "=item *" for all of them, to produce bul
lets, or use "=item 1.", "=item 2.", etc., to produce
numbered lists, or use "=item foo", "=item bar", etc.,
i.e., things that looks nothing like bullets or num
bers. If you start with bullets or numbers, stick with
them, as many formatters use the first "=item" type to
decide how to format the list.
=for
=begin
=end
For, begin, and end let you include sections that are
not interpreted as pod text, but passed directly to
particular formatters. A formatter that can utilize
that format will use the section, otherwise it will be
completely ignored. The directive "=for" specifies
that the entire next paragraph is in the format indi
cated by the first word after "=for", like this:
=for html <br>
<p> This is a raw HTML paragraph </p>
The paired commands "=begin" and "=end" work very sim
ilarly to "=for", but instead of only accepting a sin
gle paragraph, all text from "=begin" to a paragraph
with a matching "=end" are treated as a particular
format.
Here are some examples of how to use these:
=begin html
<br>Figure 1.<IMG SRC="figure1.png"><br>
=end html
=begin text
---------------
| foo |
| bar |
---------------
^^^^ Figure 1. ^^^^
=end text
Some format names that formatters currently are known
to accept include "roff", "man", "latex", "tex",
"text", and "html". (Some formatters will treat some
of these as synonyms.)
And don't forget, when using any command, that the
command lasts up until the end of the paragraph, not
the line. Hence in the examples below, you can see the
empty lines after each command to end its paragraph.
Some examples of lists include:
=over 4
=item *
First item
=item *
Second item
=back
=over 4
=item Foo()
Description of Foo function
=item Bar()
Description of Bar function
=back
Ordinary Block of Text
It will be filled, and maybe even justified. Certain
interior sequences are recognized both here and in com
mands:
I<text> Italicize text, used for emphasis or variables
B<text> Embolden text, used for switches and programs
S<text> Text contains non-breaking spaces
C<code> Render code in a typewriter font, or give some other
indication that this represents program text
L<name> A link (cross reference) to name
L<name> manual page
L<name/ident> item in manual page
L<name/"sec"> section in other manual page
L<"sec"> section in this manual page
(the quotes are optional)
L</"sec"> ditto
same as above but only 'text' is used for output.
(Text can not contain the characters '/' and '|',
and should contain matched '<' or '>')
L<text|name>
L<text|name/ident>
L<text|name/"sec">
L<text|"sec">
L<text|/"sec">
F<file> Used for filenames
X<index> An index entry
Z<> A zero-width character
E<escape> A named character (very similar to HTML escapes)
E<lt> A literal <
E<gt> A literal >
E<sol> A literal /
E<verbar> A literal |
(these are optional except in other interior
sequences and when preceded by a capital letter)
E<n> Character number n (probably in ASCII)
E<html> Some non-numeric HTML entity, such
as E<Agrave>
Most of the time, you will only need a single set of angle
brackets to delimit the beginning and end of interior
sequences. However, sometimes you will want to put a
right angle bracket (or greater-than sign '>') inside of a
sequence. This is particularly common when using a
sequence to provide a different font-type for a snippet of
code. As with all things in Perl, there is more than one
way to do it. One way is to simply escape the closing
bracket using an "E" sequence:
C<$a E<lt>=E<gt> $b>
This will produce: ""$a <=> $b""
A more readable, and perhaps more "plain" way is to use an
alternate set of delimiters that doesn't require a ">" to
be escaped. As of perl5.5.660, doubled angle brackets
("<<" and ">>") may be used if and only if there is
whitespace immediately following the opening delimiter and
immediately preceding the closing delimiter! For example,
the following will do the trick:
C<< $a <=> $b >>
In fact, you can use as many repeated angle-brackets as
you like so long as you have the same number of them in
the opening and closing delimiters, and make sure that
whitespace immediately follows the last '<' of the opening
delimiter, and immediately precedes the first '>' of the
closing delimiter. So the following will also work:
C<<< $a <=> $b >>>
C<<<< $a <=> $b >>>>
This is currently supported by pod2text (Pod::Text),
pod2man (Pod::Man), and any other pod2xxx and Pod::Xxxx
translator that uses Pod::Parser 1.093 or later.
The Intent
That's it. The intent is simplicity, not power. I wanted
paragraphs to look like paragraphs (block format), so that
they stand out visually, and so that I could run them
through fmt easily to reformat them (that's F7 in my ver
sion of vi). I wanted the translator (and not me) to
worry about whether " or ' is a left quote or a right
quote within filled text, and I wanted it to leave the
quotes alone, dammit, in verbatim mode, so I could slurp
in a working program, shift it over 4 spaces, and have it
print out, er, verbatim. And presumably in a constant
width font.
In particular, you can leave things like this verbatim in
your text:
Perl
FILEHANDLE
$variable
function()manpage(3r)
Doubtless a few other commands or sequences will need to
be added along the way, but I've gotten along surprisingly
well with just these.
Note that I'm not at all claiming this to be sufficient
for producing a book. I'm just trying to make an idiot-
proof common source for nroff, TeX, and other markup
languages, as used for online documentation. Translators
exist for pod2man (that's for nroff(1) and troff(1)),
pod2text, pod2html, pod2latex, and pod2fm.
Embedding Pods in Perl Modules
You can embed pod documentation in your Perl scripts.
Start your documentation with a "=head1" command at the
beginning, and end it with a "=cut" command. Perl will
ignore the pod text. See any of the supplied library mod
ules for examples. If you're going to put your pods at
the end of the file, and you're using an __END__ or
__DATA__ cut mark, make sure to put an empty line there
before the first pod directive.
__END__
=head1 NAME
modern - I am a modern module
If you had not had that empty line there, then the trans
lators wouldn't have seen it.
Common Pod Pitfalls
Pod translators usually will require paragraphs to be
separated by completely empty lines. If you have an
apparently empty line with some spaces on it, this can
cause odd formatting.
Translators will mostly add wording around a L<> link,
so that "L<foo(1)>" becomes "the foo(1) manpage", for
example (see pod2man for details). Thus, you
shouldn't write things like "the L<foo> manpage", if
you want the translated document to read sensibly.
If you need total control of the text used for a link
in the output use the form L<show this text|foo>
instead.
The podchecker command is provided to check pod syntax
for errors and warnings. For example, it checks for
completely blank lines in pod segments and for unknown
escape sequences. It is still advised to pass it
through one or more translators and proofread the
result, or print out the result and proofread that.
Some of the problems found may be bugs in the transla
tors, which you may or may not wish to work around.
SEE ALSO
the pod2man manpage, the PODs: Embedded Documentation
entry in the perlsyn manpage, the podchecker manpage
AUTHOR
Larry Wall
2001-03-18 perl v5.6.1 PERLPOD(1)
