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perlpod



DESCRIPTION

       Pod is a simple-to-use markup language used for writing
       documentation for Perl, Perl programs, and Perl modules.

       Translators are available for converting Pod to various
       formats like plain text, HTML, man pages, and more.

       Pod markup consists of three basic kinds of paragraphs:
       ordinary, verbatim, and command.

       Ordinary Paragraph

       Most paragraphs in your documentation will be ordinary
       blocks of text, like this one.  You can simply type in
       your text without any markup whatsoever, and with just a
       blank line before and after.  When it gets formatted, it
       will undergo minimal formatting, like being rewrapped,
       probably put into a proportionally spaced font, and maybe
       even justified.

       You can use formatting codes in ordinary paragraphs, for
       bold, italic, "code-style", hyperlinks, and more.  Such
       codes are explained in the "Formatting Codes" section,
       below.

       Verbatim Paragraph

       Verbatim paragraphs are usually used for presenting a
       codeblock or other text which does not require any special
       parsing or formatting, and which shouldn't be wrapped.

       A verbatim paragraph is distinguished by having its first
       character be a space or a tab.  (And commonly, all its
       lines begin with spaces and/or tabs.)  It should be repro­
       duced exactly, with tabs assumed to be on 8-column bound­
       aries.  There are no special formatting codes, so you
       can't italicize or anything like that.  A \ means \, and
       nothing else.

       Command Paragraph

       A command paragraph is used for special treatment of whole
       chunks of text, usually as headings or parts of lists.

       All command paragraphs (which are typically only one line
       long) start with "=", followed by an identifier, followed
       by arbitrary text that the command can use however it
       pleases.  Currently recognized commands are

           =cut
           =pod
           =begin format
           =end format
           =for format text...

       To explain them each in detail:

       "=head1 Heading Text"
       "=head2 Heading Text"
       "=head3 Heading Text"
       "=head4 Heading Text"
           Head1 through head4 produce headings, head1 being the
           highest level.  The text in the rest of this paragraph
           is the content of the heading.  For example:

             =head2 Object Attributes

           The text "Object Attributes" comprises the heading
           there.  (Note that head3 and head4 are recent addi­
           tions, not supported in older Pod translators.)  The
           text in these heading commands can use formatting
           codes, as seen here:

             =head2 Possible Values for C<$/>

           Such commands are explained in the "Formatting Codes"
           section, below.

       "=over indentlevel"
       "=item stuff..."
       "=back"
           Item, over, and back require a little more explana­
           tion:  "=over" starts a region specifically for the
           generation of a list using "=item" commands, or for
           indenting (groups of) normal paragraphs.  At the end
           of your list, use "=back" to end it.  The indentlevel
           option to "=over" indicates how far over to indent,
           generally in ems (where one em is the width of an "M"
           in the document's base font) or roughly comparable
           units; if there is no indentlevel option, it defaults
           to four.  (And some formatters may just ignore what­
           ever indentlevel you provide.)  In the stuff in "=item
           stuff...", you may use formatting codes, as seen here:

             =item Using C<$|> to Control Buffering

           Such commands are explained in the "Formatting Codes"
           section, below.

           Note also that there are some basic rules to using
           "=over" ...  "=back" regions:
               etc., to produce numbered lists; or use "=item
               foo", "=item bar", etc. -- namely, things that
               look nothing like bullets or numbers.

               If you start with bullets or numbers, stick with
               them, as formatters use the first "=item" type to
               decide how to format the list.

       "=cut"
           To end a Pod block, use a blank line, then a line
           beginning with "=cut", and a blank line after it.
           This lets Perl (and the Pod formatter) know that this
           is where Perl code is resuming.  (The blank line
           before the "=cut" is not technically necessary, but
           many older Pod processors require it.)

       "=pod"
           The "=pod" command by itself doesn't do much of any­
           thing, but it signals to Perl (and Pod formatters)
           that a Pod block starts here.  A Pod block starts with
           any command paragraph, so a "=pod" command is usually
           used just when you want to start a Pod block with an
           ordinary paragraph or a verbatim paragraph.  For exam­
           ple:

             =item stuff()

             This function does stuff.

             =cut

             sub stuff {
               ...
             }

             =pod

             Remember to check its return value, as in:

               stuff() || die "Couldn't do stuff!";

             =cut

       "=begin formatname"
       "=end formatname"
       "=for formatname text..."
           For, begin, and end will let you have regions of
           text/code/data that are not generally interpreted as
           normal Pod text, but are passed directly to particular
           formatters, or are otherwise special.  A formatter
           that can use that format will use the region, other­
           wise it will be completely ignored.
           the remainder of just this paragraph (starting right
           after formatname) is in that special format.

             =for html <hr> <img src="thang.png">
             <p> This is a raw HTML paragraph </p>

           This means the same thing as the above "=begin html"
           ... "=end html" region.

           That is, with "=for", you can have only one para­
           graph's worth of text (i.e., the text in "=foo target­
           name text..."), but with "=begin targetname" ... "=end
           targetname", you can have any amount of stuff inbe­
           tween.  (Note that there still must be a blank line
           after the "=begin" command and a blank line before the
           "=end" command.

           Here are some examples of how to use these:

             =begin html

             <br>Figure 1.<br><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.)

           A format name of "comment" is common for just making
           notes (presumably to yourself) that won't appear in
           any formatted version of the Pod document:

             =for comment
             Make sure that all the available options are documented!

           Some formatnames will require a leading colon (as in
           "=for :formatname", or "=begin :formatname" ... "=end
           :formatname"), to signal that the text is not raw
           data, but instead is Pod text (i.e., possibly contain­

             =encoding koi8-r

             =encoding ShiftJIS

             =encoding big5

       And don't forget, when using any command, that the command
       lasts up until the end of its paragraph, not its line.  So
       in the examples below, you can see that every command
       needs the blank line after it, to end its paragraph.

       Some examples of lists include:

         =over

         =item *

         First item

         =item *

         Second item

         =back

         =over

         =item Foo()

         Description of Foo function

         =item Bar()

         Description of Bar function

         =back

       Formatting Codes

       In ordinary paragraphs and in some command paragraphs,
       various formatting codes (a.k.a. "interior sequences") can
       be used:

       "I<text>" -- italic text
           Used for emphasis (""be I<careful!>"") and parameters
           (""redo I<LABEL>"")

       "B<text>" -- bold text
           Used for switches (""perl's B<-n> switch""), programs
           (""some systems provide a B<chfn> for that""), empha­
           sis (""be B<careful!>""), and so on (""and that fea­
           *   "L<name>"

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

           *   "L<name/"sec">" or "L<name/sec>"

               Link to a section in other manual page.  E.g.,
               "L<perlsyn/"For Loops">"

           *   "L</"sec">" or "L</sec>" or "L<"sec">"

               Link to a section in this manual page.  E.g.,
               "L</"Object Methods">"

           A section is started by the named heading or item.
           For example, "L<perlvar/$.>" or "L<perlvar/"$.">" both
           link to the section started by ""=item $."" in perl­
           var.  And "L<perlsyn/For Loops>" or "L<perlsyn/"For
           Loops">" both link to the section started by ""=head2
           For Loops"" in perlsyn.

           To control what text is used for display, you use
           ""L<text|...>"", as in:

           *   "L<text|name>"

               Link this text to that manual page.  E.g., "L<Perl
               Error Messages|perldiag>"

           *   "L<text|name/"sec">" or "L<text|name/sec>"

               Link this text to that section in that manual
               page.  E.g., "L<SWITCH statements|perlsyn/"Basic
               BLOCKs and Switch Statements">"

           *   "L<text|/"sec">" or "L<text|/sec>" or
               "L<text|"sec">"

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

           Or you can link to a web page:

           *   "L<scheme:...>"

               Links to an absolute URL.  For example,
               "L<http://www.perl.org/>".  But note that there is
               no corresponding "L<text|scheme:...>" syntax, for
               matting codes, notably "L<...>", and when preceded
               by a capital letter.

           *   "E<htmlname>"

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

           *   "E<number>"

               The ASCII/Latin-1/Unicode character with that num­
               ber.  A leading "0x" means that number is hex, as
               in "E<0x201E>".  A leading "0" means that number
               is octal, as in "E<075>".  Otherwise number is
               interpreted as being in decimal, as in "E<181>".

               Note that older Pod formatters might not recognize
               octal or hex numeric escapes, and that many for­
               matters cannot reliably render characters above
               255.  (Some formatters may even have to use com­
               promised renderings of Latin-1 characters, like
               rendering "E<eacute>" as just a plain "e".)

       "F<filename>" -- used for filenames
           Typically displayed in italics.  Example:
           ""F<.cshrc>""

       "S<text>" -- text contains non-breaking spaces
           This means that the words in text should not be broken
           across lines.  Example: "S<$x ? $y : $z>".

       "X<topic name>" -- an index entry
           This is ignored by most formatters, but some may use
           it for building indexes.  It always renders as
           empty-string.  Example: "X<absolutizing relative
           URLs>"

       "Z<>" -- a null (zero-effect) formatting code
           This is rarely used.  It's one way to get around using
           an E<...> code sometimes.  For example, instead of
           ""NE<lt>3"" (for "N<3") you could write ""NZ<><3""
           (the "Z<>" breaks up the "N" and the "<" so they can't
           be considered the part of a (fictitious) "N<...>"
           code.

       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
       whitespace right after the opening delimiter and whites­
       pace right before 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.  (The whitespace is ignored.)  So the
       following will also work:

           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" (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.

       The Intent

       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 "fmt" easily to reformat them (that's F7 in my
       version of vi, or Esc Q in my version of emacs).  I wanted
       the translator to always leave the "'" and "`" and """
       quotes alone, in verbatim mode, so I could slurp in a
       working program, shift it over four spaces, and have it
       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 transla­
       tors wouldn't have recognized the "=head1" as starting a
       Pod block.

       Hints for Writing Pod

       ·   The 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.

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

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

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

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

       ·   Some older Pod translators require paragraphs (includ­
           ing command paragraphs like "=head2 Functions") to be
           separated by 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.

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

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


SEE ALSO

       perlpodspec, "PODs: Embedded Documentation" in perlsyn,
       perlnewmod, perldoc, pod2html, pod2man, podchecker.


AUTHOR

       Larry Wall, Sean M. Burke

perl v5.8.1                 2003-09-02                 PERLPOD(1)
  

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