perlpod.pod

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form of computerese ("C<CE<lt>drwxr-xr-xE<gt>>").

=item C<LE<lt>nameE<gt>> -- a hyperlink
X<L> X<< LZ<><> >> X<POD, formatting code, hyperlink> X<hyperlink>

There are various syntaxes, listed below.  In the syntaxes given,
C<text>, C<name>, and C<section> cannot contain the characters
'/' and '|'; and any '<' or '>' should be matched.

=over

=item *

C<LE<lt>nameE<gt>>

Link to a Perl manual page (e.g., C<LE<lt>Net::PingE<gt>>).  Note
that C<name> should not contain spaces.  This syntax
is also occasionally used for references to UNIX man pages, as in
C<LE<lt>crontab(5)E<gt>>.

=item *

C<LE<lt>name/"sec"E<gt>> or C<LE<lt>name/secE<gt>>

Link to a section in other manual page.  E.g.,
C<LE<lt>perlsyn/"For Loops"E<gt>>

=item *

C<LE<lt>/"sec"E<gt>> or C<LE<lt>/secE<gt>> or C<LE<lt>"sec"E<gt>>

Link to a section in this manual page.  E.g.,
C<LE<lt>/"Object Methods"E<gt>>

=back

A section is started by the named heading or item.  For
example, C<LE<lt>perlvar/$.E<gt>> or C<LE<lt>perlvar/"$."E<gt>> both
link to the section started by "C<=item $.>" in perlvar.  And
C<LE<lt>perlsyn/For LoopsE<gt>> or C<LE<lt>perlsyn/"For Loops"E<gt>>
both link to the section started by "C<=head2 For Loops>"
in perlsyn.

To control what text is used for display, you
use "C<LE<lt>text|...E<gt>>", as in:

=over

=item *

C<LE<lt>text|nameE<gt>>

Link this text to that manual page.  E.g.,
C<LE<lt>Perl Error Messages|perldiagE<gt>>

=item *

C<LE<lt>text|name/"sec"E<gt>> or C<LE<lt>text|name/secE<gt>>

Link this text to that section in that manual page.  E.g.,
C<LE<lt>postfix "if"|perlsyn/"Statement Modifiers"E<gt>>

=item *

C<LE<lt>text|/"sec"E<gt>> or C<LE<lt>text|/secE<gt>>
or C<LE<lt>text|"sec"E<gt>>

Link this text to that section in this manual page.  E.g.,
C<LE<lt>the various attributes|/"Member Data"E<gt>>

=back

Or you can link to a web page:

=over

=item *

C<LE<lt>scheme:...E<gt>>

Links to an absolute URL.  For example,
C<LE<lt>http://www.perl.org/E<gt>>.  But note
that there is no corresponding C<LE<lt>text|scheme:...E<gt>> syntax, for
various reasons.

=back

=item C<EE<lt>escapeE<gt>> -- a character escape
X<E> X<< EZ<><> >> X<POD, formatting code, escape> X<escape>

Very similar to HTML/XML C<&I<foo>;> "entity references":

=over

=item *

C<EE<lt>ltE<gt>> -- a literal E<lt> (less than)

=item *

C<EE<lt>gtE<gt>> -- a literal E<gt> (greater than)

=item *

C<EE<lt>verbarE<gt>> -- a literal | (I<ver>tical I<bar>)

=item *

C<EE<lt>solE<gt>> = a literal / (I<sol>idus)

The above four are optional except in other formatting codes,
notably C<LE<lt>...E<gt>>, and when preceded by a
capital letter.

=item *

C<EE<lt>htmlnameE<gt>>

Some non-numeric HTML entity name, such as C<EE<lt>eacuteE<gt>>,
meaning the same thing as C<&eacute;> in HTML -- i.e., a lowercase
e with an acute (/-shaped) accent.

=item *

C<EE<lt>numberE<gt>>

The ASCII/Latin-1/Unicode character with that number.  A
leading "0x" means that I<number> is hex, as in
C<EE<lt>0x201EE<gt>>.  A leading "0" means that I<number> is octal,
as in C<EE<lt>075E<gt>>.  Otherwise I<number> is interpreted as being
in decimal, as in C<EE<lt>181E<gt>>.

Note that older Pod formatters might not recognize octal or
hex numeric escapes, and that many formatters cannot reliably
render characters above 255.  (Some formatters may even have
to use compromised renderings of Latin-1 characters, like
rendering C<EE<lt>eacuteE<gt>> as just a plain "e".)

=back

=item C<FE<lt>filenameE<gt>> -- used for filenames
X<F> X<< FZ<><> >> X<POD, formatting code, filename> X<filename>

Typically displayed in italics.  Example: "C<FE<lt>.cshrcE<gt>>"

=item C<SE<lt>textE<gt>> -- text contains non-breaking spaces
X<S> X<< SZ<><> >> X<POD, formatting code, non-breaking space> 
X<non-breaking space>

This means that the words in I<text> should not be broken
across lines.  Example: S<C<SE<lt>$x ? $y : $zE<gt>>>.

=item C<XE<lt>topic nameE<gt>> -- an index entry
X<X> X<< XZ<><> >> X<POD, formatting code, index entry> X<index entry>

This is ignored by most formatters, but some may use it for building
indexes.  It always renders as empty-string.
Example: C<XE<lt>absolutizing relative URLsE<gt>>

=item C<ZE<lt>E<gt>> -- a null (zero-effect) formatting code
X<Z> X<< ZZ<><> >> X<POD, formatting code, null> X<null>

This is rarely used.  It's one way to get around using an
EE<lt>...E<gt> code sometimes.  For example, instead of
"C<NEE<lt>ltE<gt>3>" (for "NE<lt>3") you could write
"C<NZE<lt>E<gt>E<lt>3>" (the "ZE<lt>E<gt>" breaks up the "N" and
the "E<lt>" so they can't be considered
the part of a (fictitious) "NE<lt>...E<gt>" code.

=for comment
 This was formerly explained as a "zero-width character".  But it in
 most parser models, it parses to nothing at all, as opposed to parsing
 as if it were a E<zwnj> or E<zwj>, which are REAL zero-width characters.
 So "width" and "character" are exactly the wrong words.

=back

Most of the time, you will need only a single set of angle brackets to
delimit the beginning and end of formatting codes.  However,
sometimes you will want to put a real right angle bracket (a
greater-than sign, '>') inside of a formatting code.  This is particularly
common when using a formatting code 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 C<E> code:

    C<$a E<lt>=E<gt> $b>

This will produce: "C<$a E<lt>=E<gt> $b>"

A more readable, and perhaps more "plain" way is to use an alternate
set of delimiters that doesn't require a single ">" to be escaped.  With
the Pod formatters that are standard starting with perl5.5.660, doubled
angle brackets ("<<" and ">>") may be used I<if and only if there is
whitespace right after the opening delimiter and whitespace right
before the closing delimiter!>  For example, the following will
do the trick:
X<POD, formatting code, escaping with multiple brackets>

    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.  (The whitespace is ignored.)  So the
following will also work:
X<POD, formatting code, escaping with multiple brackets>

    C<<< $a <=> $b >>>
    C<<<<  $a <=> $b     >>>>

And they all mean exactly the same as this:

    C<$a E<lt>=E<gt> $b>

As a further example, this means that if you wanted to put these bits of
code in C<C> (code) style:

    open(X, ">>thing.dat") || die $!
    $foo->bar();

you could do it like so:

    C<<< open(X, ">>thing.dat") || die $! >>>
    C<< $foo->bar(); >>

which is presumably easier to read than the old way:

    C<open(X, "E<gt>E<gt>thing.dat") || die $!>
    C<$foo-E<gt>bar();>

This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man),
and any other pod2xxx or Pod::Xxxx translators that use
Pod::Parser 1.093 or later, or Pod::Tree 1.02 or later.

=head2 The Intent
X<POD, intent of>

The intent is simplicity of use, not power of expression.  Paragraphs
look like paragraphs (block format), so that they stand out
visually, and so that I could run them through C<fmt> easily to reformat
them (that's F7 in my version of B<vi>, or Esc Q in my version of
B<emacs>).  I wanted the translator to always leave the C<'> and C<`> and
C<"> quotes alone, in verbatim mode, so I could slurp in a
working program, shift it over four spaces, and have it print out, er,
verbatim.  And presumably in a monospace font.

The Pod format is not necessarily sufficient for writing a book.  Pod
is just meant to be an idiot-proof common source for nroff, HTML,
TeX, and other markup languages, as used for online
documentation.  Translators exist for B<pod2text>, B<pod2html>,
B<pod2man> (that's for nroff(1) and troff(1)), B<pod2latex>, and
B<pod2fm>.  Various others are available in CPAN.


=head2 Embedding Pods in Perl Modules
X<POD, embedding>

You can embed Pod documentation in your Perl modules and scripts.
Start your documentation with an empty line, a "=head1" command at the
beginning, and end it with a "=cut" command and an empty line.  Perl
will ignore the Pod text.  See any of the supplied library modules for
examples.  If you're going to put your Pod 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 command.

  __END__

  =head1 NAME

  Time::Local - efficiently compute time from local and GMT time

Without that empty line before the "=head1", many translators wouldn't
have recognized the "=head1" as starting a Pod block.

=head2 Hints for Writing Pod

=over

=item *
X<podchecker> X<POD, validating>

The B<podchecker> command is provided for checking Pod syntax for errors
and warnings.  For example, it checks for completely blank lines in
Pod blocks and for unknown commands and formatting codes.  You should
still also pass your document 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 translators, which you may or may not
wish to work around.

=item *

If you're more familiar with writing in HTML than with writing in Pod, you
can try your hand at writing documentation in simple HTML, and converting
it to Pod with the experimental L<Pod::HTML2Pod|Pod::HTML2Pod> module,
(available in CPAN), and looking at the resulting code.  The experimental
L<Pod::PXML|Pod::PXML> module in CPAN might also be useful.

=item *

Many older Pod translators require the lines before every Pod
command and after every Pod command (including "=cut"!) to be a blank
line.  Having something like this:

 # - - - - - - - - - - - -
 =item $firecracker->boom()

 This noisily detonates the firecracker object.
 =cut
 sub boom {
 ...

...will make such Pod translators completely fail to see the Pod block
at all.

Instead, have it like this:

 # - - - - - - - - - - - -

 =item $firecracker->boom()

 This noisily detonates the firecracker object.

 =cut

 sub boom {
 ...

=item *

Some older Pod translators require paragraphs (including command
paragraphs like "=head2 Functions") to be separated by I<completely>
empty lines.  If you have an apparently empty line with some spaces
on it, this might not count as a separator for those translators, and
that could cause odd formatting.

=item *

Older translators might add wording around an LE<lt>E<gt> link, so that
C<LE<lt>Foo::BarE<gt>> may become "the Foo::Bar manpage", for example.
So you shouldn't write things like C<the LE<lt>fooE<gt>
documentation>, if you want the translated document to read sensibly
-- instead write C<the LE<lt>Foo::Bar|Foo::BarE<gt> documentation> or
C<LE<lt>the Foo::Bar documentation|Foo::BarE<gt>>, to control how the
link comes out.

=item *

Going past the 70th column in a verbatim block might be ungracefully
wrapped by some formatters.

=back

=head1 SEE ALSO

L<perlpodspec>, L<perlsyn/"PODs: Embedded Documentation">,
L<perlnewmod>, L<perldoc>, L<pod2html>, L<pod2man>, L<podchecker>.

=head1 AUTHOR

Larry Wall, Sean M. Burke

=cut