PERLPOD(1) Perl Programmers Reference Guide PERLPOD(1)

NAME
       perlpod - the Plain Old Documentation format

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, ver-
       batim, and command.

       OOrrddiinnaarryy PPaarraaggrraapphh

       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 justi-
       fied.

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

       VVeerrbbaattiimm PPaarraaggrraapphh

       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 reproduced exactly, with tabs assumed to be
       on 8-column boundaries.  There are no special formatting codes, so you
       can't italicize or anything like that.  A \ means \, and nothing else.

       CCoommmmaanndd PPaarraaggrraapphh

       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

           =head1 Heading Text
           =head2 Heading Text
           =head3 Heading Text
           =head4 Heading Text
           =over indentlevel
           =item stuff
           =back
           =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 additions, not supported in older
           Pod translators.)  The text in these heading commands can use for-
           matting 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 explanation:  "=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
           whatever 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:

           *   Don't use "=item"s outside of an "=over" ... "=back" region.

           *   The first thing after the "=over" command should be an "=item",
               unless there aren't going to be any items at all in this
               "=over" ... "=back" region.

           *   Don't put "=headn" commands inside an "=over" ... "=back"
               region.

           *   And perhaps most importantly, keep the items 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. - namely, things that look
               nothing like bullets or numbers.

               If you start with bullets or numbers, stick with them, as for-
               matters 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 anything, 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 example:

             =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, otherwise
           it will be completely ignored.

           A command "=begin formatname", some paragraphs, and a command "=end
           formatname", mean that the text/data inbetween is meant for format-
           ters that understand the special format called formatname.  For
           example,

             =begin html

             
 
             
 This is a raw HTML paragraph 

             =end html

           The command "=for formatname text..."  specifies that the remainder
           of just this paragraph (starting right after formatname) is in that
           special format.

             =for html 
 
             
 This is a raw HTML paragraph 

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

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

           Here are some examples of how to use these:

             =begin html

             
Figure 1.



             =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 (presum-
           ably 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 :format-
           name", or "=begin :formatname" ... "=end :formatname"), to signal
           that the text is not raw data, but instead is Pod text (i.e., pos-
           sibly containing formatting codes) that's just not for normal for-
           matting (e.g., may not be a normal-use paragraph, but might be for
           formatting as a footnote).

       "=encoding encodingname"
           This command is used for declaring the encoding of a document.
           Most users won't need this; but if your encoding isn't US-ASCII or
           Latin-1, then put a "=encoding encodingname" command early in the
           document so that pod formatters will know how to decode the docu-
           ment.  For encodingname, use a name recognized by the Encode::Sup-
           ported module.  Examples:

             =encoding utf8

             =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

       FFoorrmmaattttiinngg CCooddeess

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

       "I" - italic text
           Used for emphasis (""be I"") and parameters (""redo
           I"")

       "B" - bold text
           Used for switches (""perl's B<-n> switch""), programs (""some sys-
           tems provide a B for that""), emphasis (""be B""),
           and so on (""and that feature is known as B"").

       "C" - code text
           Renders code in a typewriter font, or gives some other indication
           that this represents program text (""C"") or some
           other form of computerese (""C"").

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

           *   "L"

               Link to a Perl manual page (e.g., "L").  Note that
               "name" should not contain spaces.  This syntax is also occa-
               sionally used for references to UNIX man pages, as in
               "L".

           *   "L" or "L"

               Link to a section in other manual page.  E.g., "L"

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

               Link to a section in this manual page.  E.g., "L               ods">"

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

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

           *   "L"

               Link this text to that manual page.  E.g., "L               sages|perldiag>"

           *   "L" or "L"

               Link this text to that section in that manual page.  E.g.,
               "L               ments">"

           *   "L" or "L" or "L"

               Link this text to that section in this manual page.  E.g.,
               "L"

           Or you can link to a web page:

           *   "L"

               Links to an absolute URL.  For example,
               "L".  But note that there is no corre-
               sponding "L" syntax, for various reasons.

       "E" - a character escape
           Very similar to HTML/XML "&foo;" "entity references":

           *   "E" - a literal < (less than)

           *   "E" - a literal > (greater than)

           *   "E" - a literal | (vertical bar)

           *   "E" = a literal / (solidus)

               The above four are optional except in other formatting codes,
               notably "L<...>", and when preceded by a capital letter.

           *   "E"

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

           *   "E"

               The ASCII/Latin-1/Unicode character with that number.  A lead-
               ing "0x" means that number is hex, as in "E<0x201E>".  A lead-
               ing "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 formatters cannot reliably ren-
               der characters above 255.  (Some formatters may even have to
               use compromised renderings of Latin-1 characters, like render-
               ing "E" as just a plain "e".)

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

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

       "X" - an index entry
           This is ignored by most formatters, but some may use it for build-
           ing indexes.  It always renders as empty-string.  Example: "X           lutizing 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 ""NE3"" (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 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 "E" code:

           C<$a E=E $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 single ">" to be escaped.
       With the Pod formatters that are standard starting with perl5.5.660,
       doubled angle brackets ("<<" and ">>") may be used 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:

           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=E $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:

           CEthing.dat") || die $!>
           C<$foo-Ebar();>

       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 vvii, or Esc Q in my version of eemmaaccss).  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 print out, er, verbatim.  And presum-
       ably 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.  Transla-
       tors exist for ppoodd22tteexxtt, ppoodd22hhttmmll, ppoodd22mmaann (that's for nroff(1) and
       troff(1)), ppoodd22llaatteexx, and ppoodd22ffmm.  Various others are available in
       CPAN.

       EEmmbbeeddddiinngg PPooddss iinn PPeerrll MMoodduulleess

       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.

       HHiinnttss ffoorr WWrriittiinngg PPoodd


       +o   The ppooddcchheecckkeerr 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 trans-
           lators and proofread the result, or print out the result and proof-
           read that.  Some of the problems found may be bugs in the transla-
           tors, which you may or may not wish to work around.

       +o   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 Pod::HTML2Pod mod-
           ule, (available in CPAN), and looking at the resulting code.  The
           experimental Pod::PXML module in CPAN might also be useful.

       +o   Many older Pod translators require the lines before every Pod com-
           mand 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 {
            ...

       +o   Some older Pod translators require paragraphs (including 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.

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

       +o   Going past the 70th column in a verbatim block might be ungrace-
           fully wrapped by some formatters.

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

AUTHOR       Larry Wall, Sean M. Burke



perl v5.8.6                       2004-11-05                        PERLPOD(1)