PERLPODSPEC(1perl)

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version 5.44.0 · 2 versions
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💖 PERLPODSPEC 💖

perlpodspec — Plain Old Documentation: format specification and notes

okay bestie, so this is the page for perlpodspec, and it lives in section 1 of the Perl manual. it's the full receipts on Pod ✨

🌸 DESCRIPTION 🌸

ngl this document is the detailed notes on the Pod markup language. Most people will only have to read perlpod to know how to write in Pod, but this document may answer some incidental questions to do with parsing and rendering Pod. so like, if perlpod is the vibe, this is the deep lore 🦋

In this document, "must" / "must not", "should" / "should not", and "may" have their conventional (cf. RFC 2119) meanings: "X must do Y" means that if X doesn't do Y, it's against this specification, and should really be fixed. "X should do Y" means that it's recommended, but X may fail to do Y, if there's a good reason. "X may do Y" is merely a note that X can do Y at will (although it is up to the reader to detect any connotation of "and I think it would be nice if X did Y" versus "it wouldn't really bother me if X did Y"). ✨ so basically: must = no cap mandatory, should = please but not the end of the world, may = do whatever, it's giving free choice 💅

Notably, when I say "the parser should do Y", the parser may fail to do Y, if the calling application explicitly requests that the parser not do Y. I often phrase this as "the parser should, by default, do Y." This doesn't require the parser to provide an option for turning off whatever feature Y is (like expanding tabs in verbatim paragraphs), although it implicates that such an option may be provided. 🫶

🎀 Pod Definitions 🎀

Pod is embedded in files, typically Perl source files, although you can write a file that's nothing but Pod. literally just Pod, no Perl, iconic 👑

A line in a file consists of zero or more non-newline characters, terminated by either a newline or the end of the file.

A newline sequence is usually a platform-dependent concept, but Pod parsers should understand it to mean any of CR (ASCII 13), LF (ASCII 10), or a CRLF (ASCII 13 followed immediately by ASCII 10), in addition to any other system-specific meaning. The first CR/CRLF/LF sequence in the file may be used as the basis for identifying the newline sequence for parsing the rest of the file. 🌈

A blank line is a line consisting entirely of zero or more spaces (ASCII 32) or tabs (ASCII 9), and terminated by a newline or end-of-file. A non-blank line is a line containing one or more characters other than space or tab (and terminated by a newline or end-of-file).

(Note: Many older Pod parsers did not accept a line consisting of spaces/tabs and then a newline as a blank line. The only lines they considered blank were lines consisting of no characters at all, terminated by a newline.) 🙈 so yeah, the olds were pickier, we don't do that anymore

Whitespace is used in this document as a blanket term for spaces, tabs, and newline sequences. (By itself, this term usually refers to literal whitespace. That is, sequences of whitespace characters in Pod source, as opposed to E<32>, which is a formatting code that denotes a whitespace character.) 💀 yes we really do have two whole meanings for one word, it's giving chaos

A Pod parser is a module meant for parsing Pod (regardless of whether this involves calling callbacks or building a parse tree or directly formatting it). A Pod formatter (or Pod translator) is a module or program that converts Pod to some other format (HTML, plaintext, TeX, PostScript, RTF). A Pod processor might be a formatter or translator, or might be a program that does something else with the Pod (like counting words, scanning for index points, etc.). 🧚 three different words, all lowkey related, iykyk

Pod content is contained in Pod blocks. A Pod block starts with a line that matches m/\A=[a-zA-Z]/, and continues up to the next line that matches m/\A=cut/ or up to the end of the file if there is no m/\A=cut/ line. ⭐

Note that a parser is not expected to distinguish between something that looks like pod, but is in a quoted string, such as a here document.

Within a Pod block, there are Pod paragraphs. A Pod paragraph consists of non-blank lines of text, separated by one or more blank lines.

For purposes of Pod processing, there are four types of paragraphs in a Pod block:

  • A command paragraph (also called a "directive"). The first line of this paragraph must match m/\A=[a-zA-Z]/. Command paragraphs are typically one line, as in:
=head1 NOTES

=item *

But they may span several (non-blank) lines:

=for comment
Hm, I wonder what it would look like if
you tried to write a BNF for Pod from this.

=head3 Dr. Strangelove, or: How I Learned to
Stop Worrying and Love the Bomb

Some command paragraphs allow formatting codes in their content (i.e., after the part that matches m/\A=[a-zA-Z]\S*\s*/), as in:

=head1 Did You Remember to C<use strict;>?

In other words, the Pod processing handler for head1 will apply the same processing to Did You Remember to C<use strict;>? that it would to an ordinary paragraph (i.e., formatting codes like C<...>) are parsed and presumably formatted appropriately, and whitespace in the form of literal spaces and/or tabs is not significant. 💅

  • A verbatim paragraph. The first line of this paragraph must be a literal space or tab, and this paragraph must not be inside a =begin identifier, ... =end identifier sequence unless identifier begins with a colon (:). That is, if a paragraph starts with a literal space or tab, but is inside a =begin identifier, ... =end identifier region, then it's a data paragraph, unless identifier begins with a colon. 😭 okay so the colon is doing SO much work here, remember it

Whitespace is significant in verbatim paragraphs (although, in processing, tabs are probably expanded). 🔥

  • An ordinary paragraph. A paragraph is an ordinary paragraph if its first line matches neither m/\A=[a-zA-Z]/ nor m/\A[ \t]/, and if it's not inside a =begin identifier, ... =end identifier sequence unless identifier begins with a colon (:).
  • A data paragraph. This is a paragraph that is inside a =begin identifier ... =end identifier sequence where identifier does not begin with a literal colon (:). In some sense, a data paragraph is not part of Pod at all (i.e., effectively it's "out-of-band"), since it's not subject to most kinds of Pod parsing; but it is specified here, since Pod parsers need to be able to call an event for it, or store it in some form in a parse tree, or at least just parse around it. 🦋 it's the pod-adjacent bestie, technically not pod, but we still gotta acknowledge her

For example: consider the following paragraphs:

# <- that's the 0th column

=head1 Foo

Stuff

  $foo->bar

=cut

Here, =head1 Foo and =cut are command paragraphs because the first line of each matches m/\A=[a-zA-Z]/. [space][space]$foo->bar is a verbatim paragraph, because its first line starts with a literal whitespace character (and there's no =begin...=end region around). ✨

The =begin identifier ... =end identifier commands stop paragraphs that they surround from being parsed as ordinary or verbatim paragraphs, if identifier doesn't begin with a colon. This is discussed in detail in the section "About Data Paragraphs and "=begin/=end" Regions". 👑

💖 Pod Commands 💖

okay so bestie, this section is literally here to supplement and clarify the tea from "Command Paragraph" in perlpod. These are the currently recognized Pod commands:

=head1, =head2, =head3, =head4, =head5, =head6 👑

This command is giving "the text in the remainder of the paragraph is a heading." That text may contain formatting codes. Examples:

=head1 Object Attributes

=head3 What B<Not> to Do!

Both =head5 and =head6 were added in 2020 and might not be supported on all Pod parsers. Pod::Simple 3.41 was released on October 2020 and supports both of these providing support for all Pod::Simple-based Pod parsers.

=pod 🫶

This command says this paragraph begins a Pod block. (If we are already in the middle of a Pod block, this command has no effect at all, periodt.) If there is any text in this command paragraph after =pod, it must be ignored. Examples:

=pod

This is a plain Pod paragraph.

=pod This text is ignored.

=cut ✂️

This command says this line is the end of this previously started Pod block. If there is any text after =cut on the line, it must be ignored. Examples:

=cut

=cut The documentation ends here.

=cut
# This is the first line of program text.
sub foo { # This is the second.
It is an error to try to start a Pod block with a =cut command. In that case, the Pod processor must halt parsing of the input file, and must by default emit a warning. Fr fr, that's the rule.

=over 🌸

This command says this is the start of a list/indent region. If there is any text following the =over, it must consist of only a nonzero positive numeral. The semantics of this numeral is explained in the "About =over...=back Regions" section, further below. Formatting codes are not expanded. Examples:

=over 3

=over 3.5

=over

=item 💖

This command says an item in a list begins here. Formatting codes are processed. The semantics of the (optional) text in the remainder of this paragraph are explained in the "About =over...=back Regions" section, further below. Examples:

=item

=item *

=item      *

=item 14

=item   3.

=item C<< $thing->stuff(I<dodad>) >>

=item For transporting us beyond seas to be tried for pretended
offenses

=item He is at this time transporting large armies of foreign
mercenaries to complete the works of death, desolation and
tyranny, already begun with circumstances of cruelty and perfidy
scarcely paralleled in the most barbarous ages, and totally
unworthy the head of a civilized nation.

=back 🎀

This command says this is the end of the region begun by the most recent =over command. It permits no text after the =back command. None. Zero. Nada.

=begin formatname and =begin formatname parameter 🦋

This marks the following paragraphs (until the matching =end formatname) as being for some special kind of processing. Unless formatname begins with a colon, the contained non-command paragraphs are data paragraphs. But if formatname does begin with a colon, then non-command paragraphs are ordinary paragraphs or data paragraphs. This is discussed in detail in the section "About Data Paragraphs and "=begin/=end" Regions".

It is advised that formatnames match the regexp m/\A:?[-a-zA-Z0-9_]+\z/. Everything following whitespace after the formatname is a parameter that may be used by the formatter when dealing with this region. This parameter must not be repeated in the =end paragraph. Implementors should anticipate future expansion in the semantics and syntax of the first parameter to =begin/=end/=for.

=end formatname 🌈

This marks the end of the region opened by the matching =begin formatname region. If formatname is not the formatname of the most recent open =begin formatname region, then this is an error, and must generate an error message. This is discussed in detail in the section "About Data Paragraphs and "=begin/=end" Regions".

=for formatname text... ⭐

This is synonymous with:

=begin formatname

text...

=end formatname

That is, it creates a region consisting of a single paragraph; that paragraph is to be treated as a normal paragraph if formatname begins with a :; if formatname doesn't begin with a colon, then text... will constitute a data paragraph. There is no way to use =for formatname text... to express text... as a verbatim paragraph.

=encoding encodingname 💜

This command, which should occur early in the document (at least before any non-US-ASCII data!), declares that this document is encoded in the encoding encodingname, which must be an encoding name that Encode recognizes. (Encode's list of supported encodings, in Encode::Supported, is useful here.) If the Pod parser cannot decode the declared encoding, it should emit a warning and may abort parsing the document altogether.

A document having more than one =encoding line should be considered an error. Pod processors may silently tolerate this if the not-first =encoding lines are just duplicates of the first one (e.g., if there's a =encoding utf8 line, and later on another =encoding utf8 line). But Pod processors should complain if there are contradictory =encoding lines in the same document (e.g., if there is a =encoding utf8 early in the document and =encoding big5 later). Pod processors that recognize BOMs may also complain if they see an =encoding line that contradicts the BOM (e.g., if a document with a UTF-16LE BOM has an =encoding shiftjis line).

If a Pod processor sees any command other than the ones listed above (like =head, or =haed1, or =stuff, or =cuttlefish, or =w123), that processor must by default treat this as an error. It must not process the paragraph beginning with that command, must by default warn of this as an error, and may abort the parse. A Pod parser may allow a way for particular applications to add to the above list of known commands, and to stipulate, for each additional command, whether formatting codes should be processed.

Future versions of this specification may add additional commands.

✨ Pod Formatting Codes ✨

(ok so quick history moment 🫶 — in older drafts of this doc and of perlpod, formatting codes were literally called "interior sequences", and you might still bump into that name in the docs for Pod parsers and in error messages from Pod processors. not a vibe change, just a name change, bestie.)

There are two syntaxes for formatting codes:

  • A formatting code starts with a capital letter (just US-ASCII [A-Z]) followed by a "<", any number of characters, and ending with the first matching ">". like:
That's what I<you> think!

What's C<CORE::dump()> for?

X<C<chmod> and C<unlink()> Under Different Operating Systems>
  • A formatting code starts with a capital letter (just US-ASCII [A-Z]) followed by two or more "<"'s, one or more whitespace characters, any number of characters, one or more whitespace characters, and ending with the first matching sequence of two or more ">"'s, where the number of ">"'s equals the number of "<"'s in the opening of this formatting code. like:
That's what I<< you >> think!

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

B<< $foo->bar(); >>

With this second syntax, the whitespace character(s) after the C<<< and before the >>> (or whatever letter it is) are not renderable. they don't mean "whitespace", they're literally just part of the formatting code itself. so these are all synonyms, no cap:

C<thing>
C<< thing >>
C<<           thing     >>
C<<<   thing >>>
C<<<<
thing
           >>>>

and so on, forever, the angels are singing 💅

Finally — and this is the part that trips people up — the multiple-angle-bracket form does not alter how nested formatting codes get interpreted, which means these following four example lines are identical in meaning:

B<example: C<$a E<lt>=E<gt> $b>>

B<example: C<< $a <=> $b >>>

B<example: C<< $a E<lt>=E<gt> $b >>>

B<<< example: C<< $a E<lt>=E<gt> $b >> >>>

When you're parsing Pod, a notably tricky part is correctly parsing (potentially nested!!) formatting codes. If you're implementing this, go consult the code in the parse_text routine in Pod::Parser as an example of a correct implementation. it's giving reference implementation energy.

the codes themselves 🎀

  • I<text> -- italic text See the brief discussion in "Formatting Codes" in perlpod.
  • B<text> -- bold text See the brief discussion in "Formatting Codes" in perlpod.
  • U<text> -- underline text See the brief discussion in "Formatting Codes" in perlpod.

This was added in 2024 and might not be supported on all Pod parsers. (so like... vibe check your parser first, bestie 🫶)

  • C<code> -- code text See the brief discussion in "Formatting Codes" in perlpod.
  • F<filename> -- style for filenames See the brief discussion in "Formatting Codes" in perlpod.
  • X<topic name> -- an index entry See the brief discussion in "Formatting Codes" in perlpod.

This one is unusual: most formatters completely discard this code and its content. Other formatters will render it with invisible codes that can be used in building an index of the current document. iconic behavior tbh 👑

  • Z<> -- a null (zero-effect) formatting code Discussed briefly in "Formatting Codes" in perlpod.

This one is unusual in that it should have no content. Like, a processor may complain if it sees Z<potatoes>. Whether or not it complains, the potatoes text should be ignored. potatoes? ignored. periodt. 🥔💀

  • L<name> -- a hyperlink The complicated syntaxes of this code are discussed at length in "Formatting Codes" in perlpod, and implementation details are discussed below, in "About L<...> Codes". Parsing the contents of L<content> is tricky, fr fr. Notably, the content has to be checked for whether it looks like a URL, or whether it has to be split on literal "|" and/or "/" (in the right order!!), and so on, before E<...> codes are resolved.
  • E<escape> -- a character escape See "Formatting Codes" in perlpod, and several points in "Notes on Implementing Pod Processors".
  • S<text> -- text contains non-breaking spaces This formatting code is syntactically simple, but semantically complex. What it means is that each space in the printable content of this code signifies a non-breaking space.

Consider:

C<$x ? $y    :  $z>

S<C<$x ? $y     :  $z>>

Both signify the monospace (c[ode] style) text consisting of "$x", one space, "?", one space, ":", one space, "$z". The difference is that in the latter, with the S code, those spaces are not "normal" spaces — they're non-breaking spaces. subtle but slay 💅

If a Pod processor sees any formatting code other than the ones listed above (as in N<...>, or Q<...>, etc.), that processor must by default treat this as an error. A Pod parser may allow a way for particular applications to add to the above list of known formatting codes; a Pod parser might even allow a way to stipulate, for each additional command, whether it requires some form of special processing, as L<...> does.

Future versions of this specification may add additional formatting codes. (the future is bright 🌈)

Historical note 🔥: A few older Pod processors would not see a ">" as closing a C< code if the ">" was immediately preceded by a "-". This was so that this: C<$foo->bar> would parse as equivalent to this: C<$foo-E<gt>bar> instead of as equivalent to a C formatting code containing only "$foo-", and then a "bar>" outside the C formatting code. This problem has since been solved by the addition of syntaxes like this: C<< $foo->bar >> Compliant parsers must not treat "->" as special. okay? okay. 💜

Formatting codes absolutely cannot span paragraphs. no. stop. If a code is opened in one paragraph, and no closing code is found by the end of that paragraph, the Pod parser must close that formatting code, and should complain (as in "Unterminated I code in the paragraph starting at line 123: 'Time objects are not...'"). So these two paragraphs:

I<I told you not to do this!

Don't make me say it again!>

...must not be parsed as two paragraphs in italics (with the I code starting in one paragraph and ending in another). Instead, the first paragraph should generate a warning, but that aside, the above code must parse as if it were:

I<I told you not to do this!>

Don't make me say it again!E<gt>

(In SGMLish jargon, all Pod commands are like block-level elements, whereas all Pod formatting codes are like inline-level elements. iykyk 🧚)

📝 Notes on Implementing Pod Processors 📝

The following is a long section of miscellaneous requirements and suggestions to do with Pod processing. buckle up bestie, we're going through all of it 🫶

  • Pod formatters should tolerate lines in verbatim blocks that are of any length, even if that means having to break them (possibly several times, for very long lines) to avoid text running off the side of the page. Pod formatters may warn of such line-breaking. Such warnings are particularly appropriate for lines that are over 100 characters long, which are usually not intentional. (we see you, accidental 200-char line 💀)
  • Pod parsers must recognize all of the three well-known newline formats: CR, LF, and CRLF. See perlport.
  • Pod parsers should accept input lines that are of any length.
  • Since Perl recognizes a Unicode Byte Order Mark at the start of files as signaling that the file is Unicode encoded as in UTF-16 (whether big-endian or little-endian) or UTF-8, Pod parsers should do the same. Otherwise, the character encoding should be understood as being UTF-8 if the first highbit byte sequence in the file seems valid as a UTF-8 sequence, or otherwise as CP-1252 (earlier versions of this specification used Latin-1 instead of CP-1252).

Future versions of this specification may specify how Pod can accept other encodings. Presumably treatment of other encodings in Pod parsing would be as in XML parsing: whatever the encoding declared by a particular Pod file, content is to be stored in memory as Unicode characters. ✨

  • The well known Unicode Byte Order Marks are as follows: if the file begins with the two literal byte values 0xFE 0xFF, this is the BOM for big-endian UTF-16. If the file begins with the two literal byte value 0xFF 0xFE, this is the BOM for little-endian UTF-16. On an ASCII platform, if the file begins with the three literal byte values 0xEF 0xBB 0xBF, this is the BOM for UTF-8. A mechanism portable to EBCDIC platforms is to:
my $utf8_bom = "\x{FEFF}";
utf8::encode($utf8_bom);
  • A naive, but often sufficient heuristic on ASCII platforms, for testing the first highbit byte-sequence in a BOM-less file (whether in code or in Pod!), to see whether that sequence is valid as UTF-8 (RFC 2279) is to check whether the first byte in the sequence is in the range 0xC2 - 0xFD and whether the next byte is in the range 0x80 - 0xBF. If so, the parser may conclude that this file is in UTF-8, and all highbit sequences in the file should be assumed to be UTF-8. Otherwise the parser should treat the file as being in CP-1252. (A better check, and which works on EBCDIC platforms as well, is to pass a copy of the sequence to utf8::decode() which performs a full validity check on the sequence and returns TRUE if it is valid UTF-8, FALSE otherwise. This function is always pre-loaded, is fast because it is written in C, and will only get called at most once, so you don't need to avoid it out of performance concerns. 🏎️) In the unlikely circumstance that the first highbit sequence in a truly non-UTF-8 file happens to appear to be UTF-8, one can cater to our heuristic (as well as any more intelligent heuristic) by prefacing that line with a comment line containing a highbit sequence that is clearly not valid as UTF-8. A line consisting of simply "#", an e-acute, and any non-highbit byte, is sufficient to establish this file's encoding.
  • Pod processors must treat a "=for [label] [content...]" paragraph as meaning the same thing as a "=begin [label]" paragraph, content, and an "=end [label]" paragraph. (The parser may conflate these two constructs, or may leave them distinct, in the expectation that the formatter will nevertheless treat them the same.) same vibe, different spelling 💅
  • When rendering Pod to a format that allows comments (i.e., to nearly any format other than plaintext), a Pod formatter must insert comment text identifying its name and version number, and the name and version numbers of any modules it might be using to process the Pod. Minimal examples, bestie:
%% POD::Pod2PS v3.14159, using POD::Parser v1.92

<!-- Pod::HTML v3.14159, using POD::Parser v1.92 -->
{\doccomm generated by Pod::Tree::RTF 3.14159 using Pod::Tree 1.08}

.\" Pod::Man version 3.14159, using POD::Parser version 1.92

Formatters are also totally allowed to drop in their own extra comments, bestie — like the release date of the Pod formatter program, the contact address for the author(s) of the formatter, the current time, the name of the input file, the formatting options in effect, the version of Perl used, etc. 💬

Formatters may also choose to note errors/warnings as comments — either on top of, or instead of, emitting them some other way (like messages to STDERR, or straight up dieing). 🙈

  • Pod parsers may emit warnings or error messages (think Unknown E code E<zslig>!) to STDERR — whether by printing to STDERR, or warning/carping, or dieing/croaking — but they have to allow suppressing all that STDERR output, and instead offer an option for reporting errors/warnings some other way. Options include: firing a callback, noting the errors in some attribute of the document object, some similarly unobtrusive mechanism — or honestly even just appending a Pod Errors section to the end of the parsed form of the document. Your parser, your call, just don't be loud without an off-switch. 🔇
  • When a document is exceptionally aberrant (yes, we're using that word, slay vocabulary), Pod parsers may just abort the parse. And even then, dieing/croaking is to be avoided. Where possible, the parser library may simply close the input file and add text like *** Formatting Aborted *** to the end of the (partial) in-memory document. No dramatic exits needed. 💀
  • In paragraphs where formatting codes (like E<...>, B<...>) are understood — that is, not verbatim paragraphs, but including ordinary paragraphs and command paragraphs that produce renderable text, like =head1 — literal whitespace should generally be considered "insignificant". Meaning: one literal space has the same meaning as any (nonzero) number of literal spaces, literal newlines, and literal tabs, as long as this produces no blank lines, because blank lines would terminate the paragraph. Pod parsers should compact literal whitespace in each processed paragraph, but may provide an option for overriding this (since some processing tasks don't need it), or may follow additional special rules — for example, specially treating period-space-space or period-newline sequences. 👑
  • Pod parsers should not, by default, try to coerce apostrophe (') and quote (") into smart quotes (little 9's, 66's, 99's, etc), nor try to turn backtick (`) into anything other than a single backtick character (which is distinct from an open quote character!), nor turn -- into anything but two minus signs. And they must never do any of those things to text inside C<...> formatting codes, and never ever ever to text in verbatim paragraphs. Periodt. 🚫
  • When rendering Pod to a format that has two kinds of hyphens — one that's a non-breaking hyphen, and another that's a breakable hyphen (like in object-oriented, which can split across lines as object-, newline, oriented) — formatters are encouraged to generally translate - to non-breaking hyphen, but may apply heuristics to convert some of these to breaking hyphens. 🎀
  • Pod formatters should make reasonable efforts to keep words of Perl code from being broken across lines. For real, for real: Foo::Bar in some formatting systems looks eligible for being broken across lines as Foo:: newline Bar or even Foo::- newline Bar. That should be avoided where possible, either by disabling all line-breaking in mid-word, or by wrapping particular words with internal punctuation in "don't break this across lines" codes (which in some formats may not be a single code, but might mean inserting non-breaking zero-width spaces between every pair of characters in a word). Protect the code words at all costs. 🫶
  • Pod parsers should, by default, expand tabs in verbatim paragraphs as they are processed, before passing them to the formatter or other processor. Parsers may also allow an option for overriding this.
  • Pod parsers should, by default, remove newlines from the end of ordinary and verbatim paragraphs before passing them to the formatter. Example: while the paragraph you're reading right now could be considered, in Pod source, to end with (and contain) the newline(s) that end it, it should be processed as ending with (and containing) the period character that ends this sentence.
  • Pod parsers, when reporting errors, should make some effort to report an approximate line number — like Nested E<>'s in Paragraph #52, near line 633 of Thing/Foo.pm! — instead of merely noting the paragraph number (Nested E<>'s in Paragraph #52 of Thing/Foo.pm!). Where that's problematic, the paragraph number should at least be accompanied by an excerpt from the paragraph: Nested E<>'s in Paragraph #52 of Thing/Foo.pm, which begins 'Read/write accessor for the C<interest rate> attribute...'. Give the people context. ✨
  • Pod parsers, when processing a series of verbatim paragraphs one after another, should consider them to be one large verbatim paragraph that happens to contain blank lines. Like, these two lines, which have a blank line between them:
    use Foo;

    print Foo->VERSION

should be unified into one paragraph ("\tuse Foo;\n\n\tprint Foo->VERSION") before being passed to the formatter or other processor. Parsers may also allow an option for overriding this.

While this might be too cumbersome to implement in event-based Pod parsers, it is straightforward for parsers that return parse trees. 🌈

  • Pod formatters, where feasible, are advised to avoid splitting short verbatim paragraphs (under twelve lines, say) across pages.
  • Pod parsers must treat a line with only spaces and/or tabs on it as a "blank line" — the kind such as separates paragraphs. (Some older parsers recognized only two adjacent newlines as a "blank line" but would not recognize a newline, a space, and a newline as a blank line. That is noncompliant behavior. 🙅)
  • Authors of Pod formatters/processors should make every effort to avoid writing their own Pod parser. There are already several in CPAN, with a wide range of interface styles — and one of them, Pod::Simple, comes with modern versions of Perl. Don't reinvent, bestie. 💅
  • Characters in Pod documents may be conveyed either as literals, or by number in E<n> codes, or by an equivalent mnemonic, as in E<eacute> which is exactly equivalent to E<233>. The numbers are the Latin1/Unicode values, even on EBCDIC platforms. 🦋

When referring to characters by using an E<n> numeric code, numbers in the range 32-126 refer to those well known US-ASCII characters (also defined there by Unicode, with the same meaning), which all Pod formatters must render faithfully. Characters whose E<> numbers are in the ranges 0-31 and 127-159 should not be used (neither as literals, nor as E<number> codes), except for the literal byte-sequences for newline (ASCII 13, ASCII 13 10, or ASCII 10), and tab (ASCII 9).

Numbers in the range 160-255 refer to Latin-1 characters (also defined there by Unicode, with the same meaning). Numbers above 255 should be understood to refer to Unicode characters.

  • Be warned that some formatters cannot reliably render characters outside 32-126; and many are able to handle 32-126 and 160-255, but nothing above 255. 😭 Know your formatter's limits.
  • Besides the well-known E<lt> and E<gt> codes for less-than and greater-than, Pod parsers must understand E<sol> for / (solidus, slash), and E<verbar> for | (vertical bar, pipe). Pod parsers should also understand E<lchevron> and E<rchevron> as legacy codes for characters 171 and 187, i.e., "left-pointing double angle quotation mark" = "left pointing guillemet" and "right-pointing double angle quotation mark" = "right pointing guillemet". (These look like little << and >>, and they are now preferably expressed with the HTML/XHTML codes E<laquo> and E<raquo>.) Legacy codes stay supported though, no cap. 💜
  • Pod parsers should understand all E<html> codes as defined in the entity declarations in the most recent XHTML specification at www.W3.org. Pod parsers must understand at least the entities that define characters in the range 160-255 (Latin-1). And when a Pod parser meets some unknown E<identifier> code, it shouldn't just replace it with nullstring (by default, at least) — it may instead pass it through as a string consisting of the literal characters E, less-than, identifier, greater-than. Or Pod parsers may offer the alternative option of processing those unknown E<identifier> codes by firing an event especially for such codes, or by adding a special node-type to the in-memory document tree. Such an E<identifier> may have special meaning to some processors, or some processors may choose to add them to a special error report. Choose your adventure. 🎀
  • Pod parsers must also support the XHTML codes E<quot> for character 34 (doublequote, "), E<amp> for character 38 (ampersand, &), and E<apos> for character 39 (apostrophe, ').
  • Note that in all cases of E<whatever>, whatever — whether an htmlname, or a number in any base — must consist only of alphanumeric characters. That is, whatever must match m/\A\w+\z/. So E< 0 1 2 3 > is invalid, because it contains spaces, which aren't alphanumeric characters. This presumably does not need special treatment by a Pod processor; " 0 1 2 3 " doesn't look like a number in any base, so it would presumably be looked up in the table of HTML-like names. Since there isn't (and cannot be) an HTML-like entity called " 0 1 2 3 ", this will be treated as an error. However, Pod processors may treat E< 0 1 2 3 > or E<e-acute> as syntactically invalid, potentially earning a different error message than the error message (or warning, or event) generated by a merely unknown (but theoretically valid) htmlname, as in E<qacute> [sic]. However, Pod parsers are not required to make this distinction. It's giving "best effort", and that's fine. 💖
  • Note that E<number> must not be interpreted as simply "codepoint number in the current/native character set". It always means only "the character represented by codepoint number in Unicode." (This is identical to the semantics of &#number; in XML.)
  • Okay so the tea, bestie: formatters are gonna need lookup tables that map treatable Unicode codepoints — think \xE9, the e-acute character 💃 — over to whatever escape sequences or codes the output target needs to convey them. Take a converter to *roff, for example: it would know that \xE9 (whether it's conveyed literally, or via an E<...> sequence) is to be conveyed as e\*'. And a program rendering Pod in a Mac OS application window would presumably need to know that \xE9 maps to codepoint 142 in MacRoman encoding that (at time of writing) is native for Mac OS. Such Unicode2whatever mappings are presumably already widely available for common output formats. (That said — real talk! — such mappings may be incomplete! Implementers are not expected to bend over backwards in an attempt to render Cherokee syllabics, Etruscan runes, Byzantine musical symbols, or any of the other weird things that Unicode can encode. 💀) And if a Pod document uses a character not found in such a mapping, the formatter should consider it an unrenderable character.
  • If, surprisingly, the implementor of a Pod formatter can't find a satisfactory pre-existing table mapping from Unicode characters to escapes in the target format (say, a decent table of Unicode characters to *roff escapes), then it's gonna be necessary to build such a table. If you're in this boat, start with the characters in the range 0x00A0 - 0x00FF — that's mostly the heavily used accented characters. ✨ From there, proceed (as patience permits and fastidiousness compels) through the characters that the (X)HTML standards groups judged important enough to merit mnemonics for. Those are declared in the (X)HTML specifications at the www.W3.org site. At time of writing (September 2001), the most recent entity declaration files are:
http://www.w3.org/TR/xhtml1/DTD/xhtml-lat1.ent
http://www.w3.org/TR/xhtml1/DTD/xhtml-special.ent
http://www.w3.org/TR/xhtml1/DTD/xhtml-symbol.ent

Then you can progress through any remaining notable Unicode characters in the range 0x2000-0x204D (consult the character tables at www.unicode.org), plus whatever else strikes your fancy. Example: xhtml-symbol.ent contains the entry

<!ENTITY infin    "&#8734;"> <!-- infinity, U+221E ISOtech -->

Now, mapping "infin" to the character \x{221E} will (hopefully) have already been handled by the Pod parser — but the fact that this character shows up in the file means it's reasonably important enough to stick into a formatter's table that maps from notable Unicode characters to the codes needed to render them. So for a Unicode-to-*roff mapping, for instance, this would merit the entry:

"\x{221E}" => '\(in',

It is eagerly hoped that in the future, increasing numbers of formats (and formatters) will support Unicode characters directly (as (X)HTML does with &infin;, &#8734;, or &#x221E;), reducing the need for idiosyncratic mappings of Unicode-to-my_escapes. 🫶

  • Each individual Pod formatter has to display good judgement when confronted with an unrenderable character (which is distinct from an unknown E<thing> sequence that the parser couldn't resolve to anything, renderable or not). Good practice: map Latin letters with diacritics (like E<eacute>/E<233>) to the corresponding unaccented US-ASCII letters (like a simple character 101, e). But clearly this is often not feasible, and an unrenderable character may be represented as ?, or the like. When attempting a sane fallback (as from E<233> to e), Pod formatters may reach for the %Latin1Code_to_fallback table in Pod::Escapes, or Text::Unidecode, if available.

For example, this Pod text:

magic is enabled if you set C<$Currency> to 'E<euro>'.

may be rendered as: magic is enabled if you set $Currency to '?', or as magic is enabled if you set $Currency to '[euro]', or as magic is enabled if you set $Currency to '[x20AC]', etc.

A Pod formatter may also note, in a comment or warning, a list of what unrenderable characters were encountered. 👀

  • E<...> can freely appear in any formatting code (other than inside another E<...> or inside an Z<>). So X<The E<euro>1,000,000 Solution> is valid, and so is L<The E<euro>1,000,000 Solution|Million::Euros>. 💅
  • Some Pod formatters output to formats that implement non-breaking spaces as an individual character (which we'll call "NBSP"), while others output to formats that implement non-breaking spaces just as spaces wrapped in a "don't break this across lines" code. Note that at the level of Pod, both sorts of codes can occur: Pod can contain a NBSP character (whether as a literal, or as a E<160> or E<nbsp> code); and Pod can contain S<foo I<bar> baz> codes, where "mere spaces" (character 32) in such codes are taken to represent non-breaking spaces. Pod parsers should consider supporting the optional parsing of S<foo I<bar> baz> as if it were fooNBSPI<bar>NBSPbaz, and, going the other way, the optional parsing of groups of words joined by NBSP's as if each group were in a S<...> code, so that formatters may use the representation that maps best to what the output format demands.
  • Some processors may find the S<...> code easiest to implement by replacing each space in the parse tree under the content of the S with an NBSP. But heads up: the replacement should apply not to spaces in all text, but only to spaces in printable text. (This distinction may or may not be evident in the particular tree/event model implemented by the Pod parser.) For example, consider this unusual case:
S<L</Autoloaded Functions>>

This means the space in the middle of the visible link text must not be broken across lines. In other words, it's the same as this:

L<"AutoloadedE<160>Functions"/Autoloaded Functions>

However, a misapplied space-to-NBSP replacement could (wrongly) produce something equivalent to this:

L<"AutoloadedE<160>Functions"/AutoloadedE<160>Functions>

...which is almost definitely not going to work as a hyperlink (assuming this formatter outputs a format supporting hypertext). 😭

Formatters may choose to just not support the S format code, especially in cases where the output format simply has no NBSP character/code and no code for "don't break this stuff across lines".

  • Besides the NBSP character discussed above, implementors are reminded of the existence of the other "special" character in Latin-1, the "soft hyphen" character, also known as "discretionary hyphen", i.e. E<173> = E<0xAD> = E<shy>. This character expresses an optional hyphenation point. That is, it normally renders as nothing, but may render as a "-" if a formatter breaks the word at that point. Pod formatters should, as appropriate, do one of the following: 1) render this with a code with the same meaning (e.g., \- in RTF), 2) pass it through in the expectation that the formatter understands this character as such, or 3) delete it.

For example:

sigE<shy>action
manuE<shy>script
JarkE<shy>ko HieE<shy>taE<shy>nieE<shy>mi

These signal to a formatter that if it is to hyphenate "sigaction" or "manuscript", then it should be done as "sig-[linebreak]action" or "manu-[linebreak]script" (and if it doesn't hyphenate it, then the E<shy> doesn't show up at all). And if it is to hyphenate "Jarkko" and/or "Hietaniemi", it can do so only at the points where there is a E<shy> code.

In practice, it is anticipated that this character will not be used often, but formatters should either support it, or delete it.

  • If you think you want to add a new command to Pod (like, say, a =biblio command), ask yourself whether you could get the same effect with a for or begin/end sequence: =for biblio ... or =begin biblio ... =end biblio. Pod processors that don't get =for biblio, etc, will just ignore it, whereas they might complain loudly if they see =biblio. 🗣️
  • Throughout this document, "Pod" has been the preferred spelling for the name of the documentation format. You can also use "POD" or "pod". For the documentation that is (typically) in the Pod format, you may use "pod", or "Pod", or "POD". Understanding these distinctions is useful; but obsessing over how to spell them, usually is not. 💖

💅 About L<...> Codes 💅

okay so bestie, buckle UP, because L<...> is genuinely the most complicated of all the Pod formatting codes. one lil glance at perlpod and you can tell it's the main character. ✨ the notes below should hopefully clear up what it actually means and how processors are supposed to deal with it. let's gooo 🎀

  • step one: when parsing an L<...> code, Pod parsers must tell apart at least four attributes:
    • First: the link-text. if there isn't one, this has to be undef. (like, in L<Perl Functions|perlfunc>, the link-text is Perl Functions. meanwhile in L<Time::HiRes> and even L<|Time::HiRes>, there's no link text at all. hmm, important: link text may contain formatting.)
    • Second: the possibly inferred link-text — i.e., if there was no real link text, then this is the text we'd infer in its place. (e.g., for L<Getopt::Std>, the inferred link text is Getopt::Std.)
    • Third: the name or URL, or undef if there isn't one. (e.g., in L<Perl Functions|perlfunc>, the name — also sometimes called the page — is perlfunc. in L</CAVEATS>, the name is undef.)
    • Fourth: the section (AKA "item" in the older perlpods), or undef if there isn't one. e.g., in L<Getopt::Std/DESCRIPTION>, DESCRIPTION is the section. (🚨 side note: this is not the same thing as a manpage section like the 5 in man 5 crontab. "Section Foo" in the Pod sense means the part of the text that's introduced by the heading or item whose text is Foo.)

Pod parsers may also note additional attributes, including:

  • Fifth: a flag for whether item 3 (if it's present) is a URL (like http://lists.perl.org is), in which case there should be no section attribute; a Pod name (like perldoc and Getopt::Std are); or possibly a man page name (like crontab(5) is).
  • Sixth: the raw original L<...> content, before text is split on |, /, etc., and before E<...> codes are expanded.

(the numbering above is just there so we can reference them concisely below. it is not a requirement that these get passed as an actual list or array, ok?)

For example:

L<Foo::Bar>
  =>  undef,                         # link text
      "Foo::Bar",                    # possibly inferred link text
      "Foo::Bar",                    # name
      undef,                         # section
      'pod',                         # what sort of link
      "Foo::Bar"                     # original content

L<Perlport's section on NL's|perlport/Newlines>
  =>  "Perlport's section on NL's",  # link text
      "Perlport's section on NL's",  # possibly inferred link text
      "perlport",                    # name
      "Newlines",                    # section
      'pod',                         # what sort of link
      "Perlport's section on NL's|perlport/Newlines"
                                     # original content

L<perlport/Newlines>
  =>  undef,                         # link text
      '"Newlines" in perlport',      # possibly inferred link text
      "perlport",                    # name
      "Newlines",                    # section
      'pod',                         # what sort of link
      "perlport/Newlines"            # original content

L<crontab(5)/"DESCRIPTION">
  =>  undef,                         # link text
      '"DESCRIPTION" in crontab(5)', # possibly inferred link text
      "crontab(5)",                  # name
      "DESCRIPTION",                 # section
      'man',                         # what sort of link
      'crontab(5)/"DESCRIPTION"'     # original content

L</Object Attributes>
  =>  undef,                         # link text
      '"Object Attributes"',         # possibly inferred link text
      undef,                         # name
      "Object Attributes",           # section
      'pod',                         # what sort of link
      "/Object Attributes"           # original content

L<https://www.perl.org/>
  =>  undef,                         # link text
      "https://www.perl.org/",       # possibly inferred link text
      "https://www.perl.org/",       # name
      undef,                         # section
      'url',                         # what sort of link
      "https://www.perl.org/"         # original content

L<Perl.org|https://www.perl.org/>
  =>  "Perl.org",                    # link text
      "https://www.perl.org/",       # possibly inferred link text
      "https://www.perl.org/",       # name
      undef,                         # section
      'url',                         # what sort of link
      "Perl.org|https://www.perl.org/" # original content

note that you can tell URL-links apart from anything else by the fact that they match m/\A\w+:[^:\s]\S*\z/. so L<http://www.perl.com> is a URL, but L<HTTP::Response> is not. 💀

  • when an L<...> code has no text| part, older formatters have been out here showing wild variation in how they actually display the link or cross reference. for example, L<crontab(5)> would render as "the crontab(5) manpage", or "in the crontab(5) manpage", or just "crontab(5)". the chaos of it all 😭

Pod processors must now treat text|-less links like this:

L<name>         =>  L<name|name>
L</section>     =>  L<"section"|/section>
L<name/section> =>  L<"section" in name|name/section>
  • section names might contain markup, iykyk. like, if a section starts with:
=head2 About the C<-M> Operator

or with:

=item About the C<-M> Operator

then a link to it would look like this:

L<somedoc/About the C<-M> Operator>

Formatters may choose to ignore the markup for purposes of resolving the link, and use only the renderable characters in the section name, like:

<h1><a name="About_the_-M_Operator">About the <code>-M</code>
Operator</h1>

...

<a href="somedoc#About_the_-M_Operator">About the <code>-M</code>
Operator" in somedoc</a>
  • previous versions of perlpod used to tell L<name/"section"> links apart from L<name/item> links (and their targets). these have been merged syntactically and semantically in the current specification, and "section" can now refer to either a =headn Heading Content command or to a =item Item Content command. this specification does not say what the behavior should be when a given document has several things that all seem to produce the same section identifier (e.g., in HTML, several things all producing the same anchorname in <a name="anchorname">...</a> elements). where Pod processors can control this behavior, they should use the first such anchor. that is, L<Foo/Bar> refers to the first Bar section in Foo.

but for some processors/formats this can't easily be controlled; as with the HTML example, the behavior of multiple ambiguous <a name="anchorname">...</a> is most easily just left up to browsers to decide. shrug. 🙈

  • in an L<text|...> code, text may contain formatting codes for formatting or for E<...> escapes, like:
L<B<ummE<234>stuff>|...>

for L<...> codes without a name| part, only E<...> and Z<> codes may occur. meaning: authors should not use L<B<Foo::Bar>>.

note, however, that formatting codes and Z<>'s can occur in any and all parts of an L<...> (i.e., in name, section, text, and url).

Authors must not nest L<...> codes. for example, L<The L<Foo::Bar> man page> should be treated as an error. 🚨

  • also: Pod authors may use formatting codes inside the text part of L<text|name> (and so on for L<text|/"sec">).

in other words, this is valid:

Go read L<the docs on C<$.>|perlvar/"$.">

some output formats that do allow rendering L<...> codes as hypertext might not allow the link-text to be formatted; in that case, formatters just have to ignore that formatting. it's giving "we tried". 🫶

  • at time of writing, L<name> values are of two types: either the name of a Pod page like L<Foo::Bar> (which might be a real Perl module or program in an @INC / PATH directory, or a .pod file in those places); or the name of a Unix man page, like L<crontab(5)>. in theory, L<chmod> is ambiguous between a Pod page called chmod, or the Unix man page chmod (in whatever man-section). but a string in parens, like in crontab(5), is enough to signal that what's being discussed is not a Pod page, so it's presumably a Unix man page. this distinction doesn't matter at all to many Pod processors, but some processors that render to hypertext formats might need to tell them apart so they know how to render a given L<foo> code.
  • previous versions of perlpod allowed for a L<section> syntax (like L<Object Attributes>), which was not easily distinguishable from L<name> syntax, and for L<"section"> which was only slightly less ambiguous. this syntax is no longer in the specification, and has been replaced by the L</section> syntax (where the slash was formerly optional). Pod parsers should tolerate the L<"section"> syntax, for a while at least. the suggested heuristic for distinguishing L<section> from L<name> is that if it contains any whitespace, it's a section. and Pod processors should warn about this being deprecated syntax. 👑

💖 About =over...=back Regions 💖

so bestie, =over...=back regions are the whole vibe for list-shaped structures ok. (and when i say "region" here i'm just being a collective-term girlie for literally everything from the =over to its matching =back, no cap.)

  • the non-zero numeric indentlevel in =over indentlevel ... =back is there to give the formatter a little hint, like "hey, tab over this many spaces" (ems, or units that are roughly equivalent ✨). but ngl, lots of formatters have to convert that into an absolute measurement that may not exactly match the size of spaces (or M's) in the document's base font. other formatters may just have to completely ignore the number, periodt. if there's no explicit indentlevel parameter at all, that's the same as an indentlevel value of 4. and heads up: Pod processors may complain if indentlevel is present but is not a positive number matching m/\A(\d*\.)?\d+\z/. 🙈
  • formatter authors, this one's for u 🫶 — remember that =over ... =back can map to several different constructs in your output format. like, converting Pod to (X)HTML? it can map to any of <ul>...</ul>, <ol>...</ol>, <dl>...</dl>, or <blockquote>...</blockquote>. similarly, =item can map to <li> or <dt>. so many options, main character energy fr.
  • each =over ... =back region should be one of the following, okay?
    • a region containing only =item * commands, each one followed by some number of ordinary/verbatim paragraphs, other nested =over ... =back regions, =for... paragraphs, and =begin...=end regions.

(Pod processors must tolerate a bare =item as if it were =item *.) whether * gets rendered as a literal asterisk, an o, or some kind of real bullet character is entirely up to the Pod formatter, and it may depend on the level of nesting. slay, dealer's choice 💅

  • a region containing only m/\A=item\s+\d+\.?\s*\z/ paragraphs, each one (or each group of them) followed by some number of ordinary/verbatim paragraphs, other nested =over ... =back regions, =for... paragraphs, and/or =begin...=end codes.
note: the numbers must start at 1 in each section, and must proceed in order and without skipping numbers. no jumping around, bestie, this is a line not a playlist. 🔥

(Pod processors must tolerate lines like =item 1 as if they were =item 1., with the period.)

  • a region containing only =item [text] commands, each one (or each group of them) followed by some number of ordinary/verbatim paragraphs, other nested =over ... =back regions, or =for... paragraphs, and =begin...=end regions.

the =item [text] paragraph should not match m/\A=item\s+\d+\.?\s*\z/ or m/\A=item\s+\*\s*\z/, and it also shouldn't match just m/\A=item\s*\z/. nope nope nope.

  • a region containing no =item paragraphs at all, and containing only some number of ordinary/verbatim paragraphs, and possibly also some nested =over ... =back regions, =for... paragraphs, and =begin...=end regions. an itemless =over ... =back region in Pod is equivalent in meaning to a <blockquote>...</blockquote> element in HTML. cute 🎀
also!! with all the above cases, you can figure out which type of =over ... =back you're looking at by examining the first (non-=cut, non-=pod) Pod paragraph after the =over command. iykyk.
  • Pod formatters must tolerate arbitrarily large amounts of text in the =item text... paragraph. in practice most of these are short, like:
=item For cutting off our trade with all parts of the world

but bestie they can be arbitrarily long, no joke:

=item For transporting us beyond seas to be tried for pretended
offenses

=item He is at this time transporting large armies of foreign
mercenaries to complete the works of death, desolation and
tyranny, already begun with circumstances of cruelty and perfidy
scarcely paralleled in the most barbarous ages, and totally
unworthy the head of a civilized nation.
  • Pod processors should tolerate =item * / =item number commands with no accompanying paragraph. the middle item in this one is the queen of demonstrating that:
=over

=item 1

Pick up dry cleaning.

=item 2

=item 3

Stop by the store.  Get Abba Zabas, Stoli, and cheap lawn chairs.

=back

see how =item 2 is just... there? no text, all presence. iconic.

  • no =over ... =back region can contain headings. processors may treat such a heading as an error. like, actually don't. 💀
  • also note that an =over ... =back region should have some content. that means authors should not pull an empty region like this:
=over

=back

Pod processors that see such a contentless =over ... =back region may ignore it, or may report it as an error. either way, embarrassing. 😭

  • processors must tolerate an =over list that goes off the end of the document (like, it has no matching =back at all), but they may warn about such a list. fair tbh.
  • authors of Pod formatters should note that this construct:
=item Neque

=item Porro

=item Quisquam Est

Qui dolorem ipsum quia dolor sit amet, consectetur, adipisci
velit, sed quia non numquam eius modi tempora incidunt ut
labore et dolore magnam aliquam quaerat voluptatem.

=item Ut Enim

is semantically ambiguous, in a way that makes formatting decisions a bit difficult. like, the way that this is open to interpretation?? 🙈

on the one hand, it could be a mention of an item Neque, mention of another item Porro, and mention of another item Quisquam Est, with just the last one requiring the explanatory paragraph Qui dolorem ipsum quia dolor...; and then an item Ut Enim. in that case, you'd want to format it like so:

Neque

Porro

Quisquam Est
  Qui dolorem ipsum quia dolor sit amet, consectetur, adipisci
  velit, sed quia non numquam eius modi tempora incidunt ut
  labore et dolore magnam aliquam quaerat voluptatem.

Ut Enim

but it could equally well be a discussion of three (related or equivalent) items — Neque, Porro, and Quisquam Est — followed by a paragraph explaining them all, and then a new item Ut Enim. in that case, you'd probably want to format it like so:

Neque
Porro
Quisquam Est
  Qui dolorem ipsum quia dolor sit amet, consectetur, adipisci
  velit, sed quia non numquam eius modi tempora incidunt ut
  labore et dolore magnam aliquam quaerat voluptatem.

Ut Enim

but (for the foreseeable future, bestie 💜), Pod does not provide any way for Pod authors to distinguish which grouping is meant by the above =item-cluster structure. so formatters should format it like so:

Neque

Porro

Quisquam Est

  Qui dolorem ipsum quia dolor sit amet, consectetur, adipisci
  velit, sed quia non numquam eius modi tempora incidunt ut
  labore et dolore magnam aliquam quaerat voluptatem.

Ut Enim

that is, there should be (at least roughly) equal spacing between items as between paragraphs — although that spacing may well be less than the full height of a line of text, no biggie. this leaves it to the reader to use (con)textual cues to figure out whether the Qui dolorem ipsum... paragraph applies to the Quisquam Est item or to all three items Neque, Porro, and Quisquam Est. and while that's not an ideal situation, it is preferable to providing formatting cues that may be actually contrary to the author's intent. periodt. ✨

okay bestie this is literally the last section and it's ALL about data paragraphs and =begin/=end regions 💅 sit with me, we're almost done

Data paragraphs are typically used for inlining non-Pod data that's gonna be used (typically passed through) when rendering the document to a specific format:

=begin rtf

\par{\pard\qr\sa4500{\i Printed\~\chdate\~\chtime}\par}

=end rtf

The exact same effect could, incidentally, be achieved with a single =for paragraph:

=for rtf \par{\pard\qr\sa4500{\i Printed\~\chdate\~\chtime}\par}

(Although that's not formally a data paragraph, it has the same meaning as one, and Pod parsers may parse it as one. okay noted 😌)

Another example of a data paragraph:

=begin html

I like <em>PIE</em>!

<hr>Especially pecan pie!

=end html

Now here's the tea: if these were ordinary paragraphs, the Pod parser would try to expand the E</em> (in the first paragraph) as a formatting code, just like E<lt> or E<eacute>. But since this is inside a =begin identifier...=end identifier region and the identifier html doesn't have a : prefix, the contents of this region are stored as data paragraphs, instead of being processed as ordinary paragraphs (or if they began with spaces and/or tabs, as verbatim paragraphs). 🫶

As a further example: at time of writing, no biblio identifier is supported, but suppose some processor were written to recognize it as a way of (say) denoting a bibliographic reference (necessarily containing formatting codes in ordinary paragraphs). The fact that biblio paragraphs were meant for ordinary processing would be indicated by prefacing each biblio identifier with a colon:

=begin :biblio

Wirth, Niklaus.  1976.  I<Algorithms + Data Structures =
Programs.>  Prentice-Hall, Englewood Cliffs, NJ.

=end :biblio

This would signal to the parser that paragraphs in this begin...end region are subject to normal handling as ordinary/verbatim paragraphs (while still tagged as meant only for processors that understand the biblio identifier). The same effect could be had with:

=for :biblio
Wirth, Niklaus.  1976.  I<Algorithms + Data Structures =
Programs.>  Prentice-Hall, Englewood Cliffs, NJ.

The : on these identifiers means simply "process this stuff normally, even though the result will be for some special target". The author suggests that parser APIs report biblio as the target identifier, but also report that it had a : prefix. (And similarly, with the above html, report html as the target identifier, and note the lack of a : prefix.) ✨

Note that a =begin identifier...=end identifier region where identifier begins with a colon can contain commands. For example:

=begin :biblio

Wirth's classic is available in several editions, including:

=for comment
 hm, check abebooks.com for how much used copies cost.

=over

=item

Wirth, Niklaus.  1975.  I<Algorithmen und Datenstrukturen.>
Teubner, Stuttgart.  [Yes, it's in German.]

=item

Wirth, Niklaus.  1976.  I<Algorithms + Data Structures =
Programs.>  Prentice-Hall, Englewood Cliffs, NJ.

=back

=end :biblio

Note, however, that a =begin identifier...=end identifier region where identifier does not begin with a colon should not directly contain =head1 ... =head4 commands, nor =over, nor =back, nor =item. For example, this may be considered invalid:

=begin somedata

This is a data paragraph.

=head1 Don't do this!

This is a data paragraph too.

=end somedata

A Pod processor may signal that the above (specifically the =head1 paragraph) is an error. Note, however, that the following should not be treated as an error:

=begin somedata

This is a data paragraph.

=cut

# Yup, this isn't Pod anymore.
sub excl { (rand() > .5) ? "hoo!" : "hah!" }

=pod

This is a data paragraph too.

=end somedata

And this too is valid:

=begin someformat

This is a data paragraph.

  And this is a data paragraph.

=begin someotherformat

This is a data paragraph too.

  And this is a data paragraph too.

=begin :yetanotherformat

=head2 This is a command paragraph!

This is an ordinary paragraph!

  And this is a verbatim paragraph!

=end :yetanotherformat

=end someotherformat

Another data paragraph!

=end someformat

The contents of the above =begin :yetanotherformat ... =end :yetanotherformat region aren't data paragraphs, because the immediately containing region's identifier (:yetanotherformat) begins with a colon. In practice, most regions that contain data paragraphs will contain only data paragraphs; however, the above nesting is syntactically valid as Pod, even if it is rare. However, the handlers for some formats, like html, will accept only data paragraphs, not nested regions; and they may complain if they see (targeted for them) nested regions, or commands, other than =end, =pod, and =cut. 🙈

Also consider this valid structure:

=begin :biblio

Wirth's classic is available in several editions, including:

=over

=item

Wirth, Niklaus.  1975.  I<Algorithmen und Datenstrukturen.>
Teubner, Stuttgart.  [Yes, it's in German.]

=item

Wirth, Niklaus.  1976.  I<Algorithms + Data Structures =
Programs.>  Prentice-Hall, Englewood Cliffs, NJ.

=back

Buy buy buy!

=begin html

<img src='wirth_spokesmodeling_book.png'>

<hr>

=end html

Now now now!

=end :biblio

There, the =begin html...=end html region is nested inside the larger =begin :biblio...=end :biblio region. Note that the content of the =begin html...=end html region is data paragraph(s), because the immediately containing region's identifier (html) doesn't begin with a colon. 🌈

Pod parsers, when processing a series of data paragraphs one after another (within a single region), should consider them to be one large data paragraph that happens to contain blank lines. So the content of the above =begin html...=end html may be stored as two data paragraphs (one consisting of <img src='wirth_spokesmodeling_book.png'>\n and another consisting of <hr>\n), but should be stored as a single data paragraph (consisting of <img src='wirth_spokesmodeling_book.png'>\n\n<hr>\n). 🧚

Pod processors should tolerate empty =begin something...=end something regions, empty =begin :something...=end :something regions, and contentless =for something and =for :something paragraphs. I.e., these should be tolerated:

=for html

=begin html

=end html

=begin :biblio

=end :biblio

Incidentally, note that there's no easy way to express a data paragraph starting with something that looks like a command. Consider:

=begin stuff

=shazbot

=end stuff

There, =shazbot will be parsed as a Pod command shazbot, not as a data paragraph =shazbot\n. However, you can express a data paragraph consisting of =shazbot\n using this code:

=for stuff =shazbot

The situation where this is necessary, is presumably quite rare. 💀

Note that =end commands must match the currently open =begin command. That is, they must properly nest. For example, this is valid:

=begin outer

X

=begin inner

Y

=end inner

Z

=end outer

while this is invalid:

=begin outer

X

=begin inner

Y

=end outer

Z

=end inner

This latter is improper because when the =end outer command is seen, the currently open region has the formatname inner, not outer. (It just happens that outer is the format name of a higher-up region.) This is an error. Processors must by default report this as an error, and may halt processing the document containing that error. A corollary of this is that regions cannot "overlap". That is, the latter block above does not represent a region called outer which contains X and Y, overlapping a region called inner which contains Y and Z. But because it is invalid (as all apparently overlapping regions would be), it doesn't represent that, or anything at all. 😭

Similarly, this is invalid:

=begin thing

=end hting

This is an error because the region is opened by thing, and the =end tries to close hting [sic].

This is also invalid:

=begin thing

=end

This is invalid because every =end command must have a formatname parameter.

🌸 SEE ALSO 🌸

  • perlpod
  • "PODs: Embedded Documentation" in perlsyn
  • podchecker

👑 AUTHOR 👑

Sean M. Burke

and that's a wrap bestie, you literally just read the whole entire page 🌟 this part came to you from perl v5.44.0, dated 2026-10-17, and it's the PERLPODSPEC(1perl) page 💖 go write some absolutely iconic Pod, you ate 💅✨

📦 where this page comes from