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database/perl/lib/pods/perlpod.pod
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database/perl/lib/pods/perlpod.pod
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=for comment
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This document is in Pod format. To read this, use a Pod formatter,
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like "perldoc perlpod".
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=head1 NAME
|
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X<POD> X<plain old documentation>
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perlpod - the Plain Old Documentation format
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=head1 DESCRIPTION
|
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|
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Pod is a simple-to-use markup language used for writing documentation
|
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for Perl, Perl programs, and Perl modules.
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|
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Translators are available for converting Pod to various formats
|
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like plain text, HTML, man pages, and more.
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|
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Pod markup consists of three basic kinds of paragraphs:
|
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L<ordinary|/"Ordinary Paragraph">,
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L<verbatim|/"Verbatim Paragraph">, and
|
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L<command|/"Command Paragraph">.
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|
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=head2 Ordinary Paragraph
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X<POD, ordinary paragraph>
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|
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Most paragraphs in your documentation will be ordinary blocks
|
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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
|
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font, and maybe even justified.
|
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|
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You can use formatting codes in ordinary paragraphs, for B<bold>,
|
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I<italic>, C<code-style>, L<hyperlinks|perlfaq>, and more. Such
|
||||
codes are explained in the "L<Formatting Codes|/"Formatting Codes">"
|
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section, below.
|
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|
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|
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=head2 Verbatim Paragraph
|
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X<POD, verbatim paragraph> X<verbatim>
|
||||
|
||||
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.
|
||||
|
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|
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=head2 Command Paragraph
|
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X<POD, command>
|
||||
|
||||
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
|
||||
|
||||
=pod
|
||||
=head1 Heading Text
|
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=head2 Heading Text
|
||||
=head3 Heading Text
|
||||
=head4 Heading Text
|
||||
=over indentlevel
|
||||
=item stuff
|
||||
=back
|
||||
=begin format
|
||||
=end format
|
||||
=for format text...
|
||||
=encoding type
|
||||
=cut
|
||||
|
||||
To explain them each in detail:
|
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|
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=over
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|
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=item C<=head1 I<Heading Text>>
|
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X<=head1> X<=head2> X<=head3> X<=head4>
|
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X<head1> X<head2> X<head3> X<head4>
|
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|
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=item C<=head2 I<Heading Text>>
|
||||
|
||||
=item C<=head3 I<Heading Text>>
|
||||
|
||||
=item C<=head4 I<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.
|
||||
The text in these heading commands can use formatting codes, as seen here:
|
||||
|
||||
=head2 Possible Values for C<$/>
|
||||
|
||||
Such commands are explained in the
|
||||
"L<Formatting Codes|/"Formatting Codes">" section, below.
|
||||
|
||||
=item C<=over I<indentlevel>>
|
||||
X<=over> X<=item> X<=back> X<over> X<item> X<back>
|
||||
|
||||
=item C<=item I<stuff...>>
|
||||
|
||||
=item C<=back>
|
||||
|
||||
Item, over, and back require a little more explanation: "=over" starts
|
||||
a region specifically for the generation of a list using "=item"
|
||||
commands, or for indenting (groups of) normal paragraphs. At the end
|
||||
of your list, use "=back" to end it. The I<indentlevel> option to
|
||||
"=over" indicates how far over to indent, generally in ems (where
|
||||
one em is the width of an "M" in the document's base font) or roughly
|
||||
comparable units; if there is no I<indentlevel> option, it defaults
|
||||
to four. (And some formatters may just ignore whatever I<indentlevel>
|
||||
you provide.) In the I<stuff> in C<=item I<stuff...>>, you may
|
||||
use formatting codes, as seen here:
|
||||
|
||||
=item Using C<$|> to Control Buffering
|
||||
|
||||
Such commands are explained in the
|
||||
"L<Formatting Codes|/"Formatting Codes">" section, below.
|
||||
|
||||
Note also that there are some basic rules to using "=over" ...
|
||||
"=back" regions:
|
||||
|
||||
=over
|
||||
|
||||
=item *
|
||||
|
||||
Don't use "=item"s outside of an "=over" ... "=back" region.
|
||||
|
||||
=item *
|
||||
|
||||
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.
|
||||
|
||||
=item *
|
||||
|
||||
Don't put "=headI<n>" commands inside an "=over" ... "=back" region.
|
||||
|
||||
=item *
|
||||
|
||||
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 have a list that contains both: 1) things that don't
|
||||
look like bullets nor numbers, plus 2) things that do, you should
|
||||
preface the bullet- or number-like items with C<ZE<lt>E<gt>>. See
|
||||
L<ZE<lt>E<gt>|/ZE<lt>E<gt> -- a null (zero-effect) formatting code>
|
||||
below for an example.)
|
||||
|
||||
If you start with bullets or numbers, stick with them, as
|
||||
formatters use the first "=item" type to decide how to format the
|
||||
list.
|
||||
|
||||
=back
|
||||
|
||||
=item C<=cut>
|
||||
X<=cut> X<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.)
|
||||
|
||||
=item C<=pod>
|
||||
X<=pod> X<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 I<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
|
||||
|
||||
=item C<=begin I<formatname>>
|
||||
X<=begin> X<=end> X<=for> X<begin> X<end> X<for>
|
||||
|
||||
=item C<=end I<formatname>>
|
||||
|
||||
=item C<=for I<formatname> I<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 I<formatname>", some paragraphs, and a
|
||||
command "=end I<formatname>", mean that the text/data in between
|
||||
is meant for formatters that understand the special format
|
||||
called I<formatname>. For example,
|
||||
|
||||
=begin html
|
||||
|
||||
<hr> <img src="thang.png">
|
||||
<p> This is a raw HTML paragraph </p>
|
||||
|
||||
=end html
|
||||
|
||||
The command "=for I<formatname> I<text...>"
|
||||
specifies that the remainder of just this paragraph (starting
|
||||
right after I<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 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 in between. (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 I<formatnames> will require a leading colon (as in
|
||||
C<"=for :formatname">, or
|
||||
C<"=begin :formatname" ... "=end :formatname">),
|
||||
to signal that the text is not raw data, but instead I<is> Pod text
|
||||
(i.e., possibly containing formatting codes) that's just not for
|
||||
normal formatting (e.g., may not be a normal-use paragraph, but might
|
||||
be for formatting as a footnote).
|
||||
|
||||
=item C<=encoding I<encodingname>>
|
||||
X<=encoding> X<encoding>
|
||||
|
||||
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,
|
||||
then put a C<=encoding I<encodingname>> command very early in the document so
|
||||
that pod formatters will know how to decode the document. For
|
||||
I<encodingname>, use a name recognized by the L<Encode::Supported>
|
||||
module. Some pod formatters may try to guess between a Latin-1 or
|
||||
CP-1252 versus
|
||||
UTF-8 encoding, but they may guess wrong. It's best to be explicit if
|
||||
you use anything besides strict ASCII. Examples:
|
||||
|
||||
=encoding latin1
|
||||
|
||||
=encoding utf8
|
||||
|
||||
=encoding koi8-r
|
||||
|
||||
=encoding ShiftJIS
|
||||
|
||||
=encoding big5
|
||||
|
||||
C<=encoding> affects the whole document, and must occur only once.
|
||||
|
||||
=back
|
||||
|
||||
And don't forget, all commands but C<=encoding> last up
|
||||
until the end of its I<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. (And some older Pod translators
|
||||
may require the C<=encoding> line to have a following blank line as
|
||||
well, even though it should be legal to omit.)
|
||||
|
||||
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
|
||||
|
||||
|
||||
=head2 Formatting Codes
|
||||
X<POD, formatting code> X<formatting code>
|
||||
X<POD, interior sequence> X<interior sequence>
|
||||
|
||||
In ordinary paragraphs and in some command paragraphs, various
|
||||
formatting codes (a.k.a. "interior sequences") can be used:
|
||||
|
||||
=for comment
|
||||
"interior sequences" is such an opaque term.
|
||||
Prefer "formatting codes" instead.
|
||||
|
||||
=over
|
||||
|
||||
=item C<IE<lt>textE<gt>> -- italic text
|
||||
X<I> X<< IZ<><> >> X<POD, formatting code, italic> X<italic>
|
||||
|
||||
Used for emphasis ("C<be IE<lt>careful!E<gt>>") and parameters
|
||||
("C<redo IE<lt>LABELE<gt>>")
|
||||
|
||||
=item C<BE<lt>textE<gt>> -- bold text
|
||||
X<B> X<< BZ<><> >> X<POD, formatting code, bold> X<bold>
|
||||
|
||||
Used for switches ("C<perl's BE<lt>-nE<gt> switch>"), programs
|
||||
("C<some systems provide a BE<lt>chfnE<gt> for that>"),
|
||||
emphasis ("C<be BE<lt>careful!E<gt>>"), and so on
|
||||
("C<and that feature is known as BE<lt>autovivificationE<gt>>").
|
||||
|
||||
=item C<CE<lt>codeE<gt>> -- code text
|
||||
X<C> X<< CZ<><> >> X<POD, formatting code, code> X<code>
|
||||
|
||||
Renders code in a typewriter font, or gives some other indication that
|
||||
this represents program text ("C<CE<lt>gmtime($^T)E<gt>>") or some other
|
||||
form of computerese ("C<CE<lt>drwxr-xr-xE<gt>>").
|
||||
|
||||
=item C<LE<lt>nameE<gt>> -- a hyperlink
|
||||
X<L> X<< LZ<><> >> X<POD, formatting code, hyperlink> X<hyperlink>
|
||||
|
||||
There are various syntaxes, listed below. In the syntaxes given,
|
||||
C<text>, C<name>, and C<section> cannot contain the characters
|
||||
'/' and '|'; and any '<' or '>' should be matched.
|
||||
|
||||
=over
|
||||
|
||||
=item *
|
||||
|
||||
C<LE<lt>nameE<gt>>
|
||||
|
||||
Link to a Perl manual page (e.g., C<LE<lt>Net::PingE<gt>>). Note
|
||||
that C<name> should not contain spaces. This syntax
|
||||
is also occasionally used for references to Unix man pages, as in
|
||||
C<LE<lt>crontab(5)E<gt>>.
|
||||
|
||||
=item *
|
||||
|
||||
C<LE<lt>name/"sec"E<gt>> or C<LE<lt>name/secE<gt>>
|
||||
|
||||
Link to a section in other manual page. E.g.,
|
||||
C<LE<lt>perlsyn/"For Loops"E<gt>>
|
||||
|
||||
=item *
|
||||
|
||||
C<LE<lt>/"sec"E<gt>> or C<LE<lt>/secE<gt>>
|
||||
|
||||
Link to a section in this manual page. E.g.,
|
||||
C<LE<lt>/"Object Methods"E<gt>>
|
||||
|
||||
=back
|
||||
|
||||
A section is started by the named heading or item. For
|
||||
example, C<LE<lt>perlvar/$.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>>
|
||||
|
||||
C<LE<lt>text|scheme:...E<gt>>
|
||||
|
||||
Links to an absolute URL. For example, C<LE<lt>http://www.perl.org/E<gt>> or
|
||||
C<LE<lt>The Perl Home Page|http://www.perl.org/E<gt>>.
|
||||
|
||||
=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<é> 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/CP-1252 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).
|
||||
|
||||
Another use is to indicate that I<stuff> in C<=item ZE<lt>E<gt>I<stuff...>>
|
||||
is not to be considered to be a bullet or number. For example,
|
||||
without the C<ZE<lt>E<gt>>, the line
|
||||
|
||||
=item Z<>500 Server error
|
||||
|
||||
could possibly be parsed as an item in a numbered list when it isn't
|
||||
meant to be.
|
||||
|
||||
Still another use is to maintain visual space between C<=item> lines.
|
||||
If you specify
|
||||
|
||||
=item foo
|
||||
|
||||
=item bar
|
||||
|
||||
it will typically get rendered as
|
||||
|
||||
foo
|
||||
bar
|
||||
|
||||
That may be what you want, but if what you really want is
|
||||
|
||||
foo
|
||||
|
||||
bar
|
||||
|
||||
you can use C<ZE<lt>E<gt>> to accomplish that
|
||||
|
||||
=item foo
|
||||
|
||||
Z<>
|
||||
|
||||
=item bar
|
||||
|
||||
=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.
|
||||
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>
|
||||
|
||||
The multiple-bracket form does not affect the interpretation of the contents of
|
||||
the formatting code, only how it must end. That means that the examples above
|
||||
are also 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. The
|
||||
B<perl> executable will ignore the Pod text. You can place a Pod
|
||||
statement where B<perl> expects the beginning of a new statement, but
|
||||
not within a statement, as that would result in an error. 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 C<__END__> or C<__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
|
||||
Reference in New Issue
Block a user