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PERLPOD

Section: Perl Programmers Reference Guide (1)
Updated: perl 5.004, patch 04
Index 

NAME

perlpod - 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 arethree kinds of paragraphs:

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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 nospecial formatting escapes, so you can't italicize or anythinglike that. A \ means \, and nothing else.

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A command. All command paragraphs start with ``='', followed by anidentifier, followed by arbitrary text that the command canuse however it pleases. Currently recognized commands are

    =head1 heading    =head2 heading    =item text    =over N    =back    =cut    =pod    =for X    =begin X    =end X

The ``=pod'' directive does nothing beyond telling the compiler to layoff parsing code through the next ``=cut''. It's useful for addinganother paragraph to the doc if you're mixing up code and pod a lot.

Head1 and head2 produce first and second level headings, with the text inthe same paragraph as the ``=headn'' directive forming the heading description.

Item, over, and back require a little more explanation: ``=over'' starts asection specifically for the generation of a list using ``=item'' commands. Atthe 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.This should probably be a default. Note also that there are some basic rulesto using =item: don't use them outside of an =over/=back block, use at leastone inside an =over/=back block, you don't _have_ to include the =back ifthe list just runs off the document, and perhaps most importantly, keep theitems consistent: either use ``=item *'' for all of them, to produce bullets,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 bulletsor numbers. If you start with bullets or numbers, stick with them, as manyformatters use the first ``=item'' type to decide how to format the list.

For, begin, and end let you include sections that are not interpretedas pod text, but passed directly to particular formatters. A formatterthat can utilize that format will use the section, otherwise it will becompletely ignored. The directive ``=for'' specifies that the entire nextparagraph is in the format indicated 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 similarly to ``=for'', butinstead of only accepting a single paragraph, all text from ``=begin'' to aparagraph 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 willtreat some of these as synonyms.)

And don't forget, when using any command, that the command lasts up untilthe end of the paragraph, not the line. Hence in the examples below, youcan 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

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An ordinary block of text. It will be filled, and maybe evenjustified. Certain interior sequences are recognized bothhere and in commands:

    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>     literal code    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    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 >                    (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>

That's it. The intent is simplicity, not power. I wanted paragraphsto look like paragraphs (block format), so that they stand outvisually, and so that I could run them through fmt easily to reformatthem (that's F7 in my version of vi). I wanted the translator (and notme) to worry about whether `` or ` is a left quote or a right quotewithin filled text, and I wanted it to leave the quotes alone, dammit, inverbatim mode, so I could slurp in a working program, shift it over 4spaces, and have it print out, er, verbatim. And presumably in aconstant 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 alongthe 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 abook. 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)),pod2html, pod2latex, and pod2fm. 

Embedding Pods in Perl Modules

You can embed pod documentation in your Perl scripts. Start yourdocumentation with a ``=head1'' command at the beginning, and end itwith a ``=cut'' command. Perl will ignore the pod text. See any of thesupplied library modules for examples. If you're going to put yourpods 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 poddirective.

    __END__

    =head1 NAME

    modern - I am a modern module

If you had not had that empty line there, then the translators wouldn'thave seen it. 

Common Pod Pitfalls

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Pod translators usually will require paragraphs to be separated bycompletely empty lines. If you have an apparently empty line withsome spaces on it, this can cause odd formatting.

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Translators will mostly add wording around a L<> link, so thatL<foo(1)> becomes ``the foo(1) manpage'', for example (seepod2man for details). Thus, you shouldn't write things like theL<foo> manpage, if you want the translated document to readsensibly.

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The script pod/checkpods.PL in the Perl source distributionprovides skeletal checking for lines that look empty but aren'tonly, but is there as a placeholder until someone writesPod::Checker. The best way to check your pod is to pass it throughone or more translators and proofread the result, or print out theresult and proofread that. Some of the problems found may be bugs inthe translators, which you may or may not wish to work around.

 

SEE ALSO

the pod2man manpage and the section on PODs: Embedded Documentation in the perlsyn manpage 

AUTHOR

Larry Wall

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Index

NAME

DESCRIPTION

Embedding Pods in Perl Modules

Common Pod Pitfalls

SEE ALSO

AUTHOR

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