Synopsis_26 - Documentation
Damian Conway <damian@conway.org>
Maintainer: Damian Conway
Date: 9 Apr 2005
Last Modified: 25 Apr 2007
Perldoc is an easy-to-use markup language with a simple, consistent underlying document object model. Perldoc can be used for writing language documentation, for documenting programs and modules, as well as for other types of document composition.
Perldoc allows for multiple syntactic dialects, all of which map onto the same set of standard document objects. The standard dialect is named "Pod".
Pod is an evolution of Perl 5's Plain Ol' Documentation (POD) markup. Compared to Perl 5 POD, Perldoc's Pod dialect is much more uniform, somewhat more compact, and considerably more expressive. The Pod dialect also differs in that it is a purely descriptive mark-up notation, with no presentational components.
Pod documents are specified using directives, which are used to declare configuration information and to delimit blocks of textual content. Every directive starts with an equals sign (=) in the first column.
The content of a document is specified within one or more blocks. Every Pod block may be declared in any of three equivalent forms: delimited style, paragraph style, or abbreviated style.
Anything in a document that is neither a Pod directive nor contained within a Pod block is treated as "ambient" material. Typically this would be the source code of the program that the Pod is documenting. Pod parsers still parse this text into the internal representation of the file (representing it as a Perldoc::Block::Ambient block), but renderers will usually ignore such blocks.
In Perl 5's POD format, once a POD directive is encountered, the parser considers everything that follows to be POD, until an explicit =cut directive is encountered, at which point the parser flips between POD and ambient text. The Perl 6 Pod format is different. A Pod parser always reverts to "ambient" at the end of each Pod directive or block. To cause the parser to remain in Pod mode, you must enclose the desired Pod region in a pod block:
=head1 A heading
This is Pod too. Specifically, this is a simple C<para> block
$this = pod('also'); # Specifically, a code block
B<=end pod>
=end code
Alternatively you can indicate an entire file contains only Pod, by giving it a .pod suffix.
Delimited blocks are bounded by =begin and =end markers, both of which are followed by a valid identifierA valid identifier is a sequence of alphanumerics and/or underscores, beginning with an alphabetic or underscore, which is the typename of the block. Typenames that are entirely lowercase (for example: =begin head1) or entirely uppercase (for example: =begin SYNOPSIS) are reserved.
After the typename, the rest of the =begin marker line is treated as configuration information for the block. This information is used in different ways by different types of blocks, but is always specified using Perl6-ish option pairs. That is, any of:
All option keys and values must, of course, be constants since Perldoc is a specification language, not a programming language. See Synopsis 2 for details of the various Perl 6 pair notations.
The configuration section may be extended over subsequent lines by starting those lines with an = in the first column followed by a whitespace character.
The lines following the opening delimiter and configuration are the data or contents of the block, which continue until the block's =end marker line. For most block types, these contents may be indented if you wish, without them being treated as code blocks. Unlike Perl 5, indented text is only treated as code within =pod, =nested, =item, =code, and semantic blocks.
The general syntax is:
For example:
=begin table :caption<Table of Contents>
Constants 1
Variables 10
Subroutines 33
Everything else 57
=end table
=begin Name :required
= :width(50)
The applicant's full name
=end Name
=begin Contact :optional
The applicant's contact details
=end Contact
Note that no blank lines are required around the directives; blank lines within the contents are always treated as part of the contents. This is a universal feature of Pod.
Note also that in the following specifications, a "blank line" is a line that is either empty or that contains only whitespace characters. That is, a blank line matches the Perl 6 pattern: /^^ \h* $$/. Pod uses blank lines as delimiters, rather than empty lines, the principle of least surprise.
Paragraph blocks are introduced by a =for marker and terminated by the next Pod directive or the first blank line (which is not considered to be part of the block's contents). The =for marker is followed by the name of the block and optional configuration information. The general syntax is:
For example:
=for table :caption<Table of Contents>
Constants 1
Variables 10
Subroutines 33
Everything else 57
=for Name :required
= :width(50)
The applicant's full name
=for Contact :optional
The applicant's contact details
Abbreviated blocks are introduced by an '=' sign in the first column, which is followed immediately by the typename of the block. The rest of the line is treated as block data, rather than as configuration. The content terminates at the next Pod directive or the first blank line (which is not part of the block data). The general syntax is:
For example:
=table
Constants 1
Variables 10
Subroutines 33
Everything else 57
=Name The applicant's full name
=Contact The applicant's contact details
Note that abbreviated blocks cannot specify configuration information. If configuration is required, use a =for or =begin/=end instead.
The three block specifications (delimited, paragraph, and abbreviated) are treated identically by the underlying documentation model, so you can use whichever form is most convenient for a particular documentation task. In the descriptions that follow, the abbreviated form will generally be used, but should be read as standing for all three forms equally.
For example, although #Headings shows only:
=head1 Top Level Heading
this automatically implies that you could also write that block as:
=for head1
Top Level Heading
or:
=begin head1
Top Level Heading
=end head1
Pod predefines a small number of standard configuration options that can be applied uniformly to built-in block types. These include:
This option specifies that the block is to be nested within its current context. For example, nesting might be applied to block quotes, to textual examples, or to commentaries. In addition the =code, =item, =input, and =output blocks all have implicit nesting.
Nesting of blocks is usually rendered by adding extra indentation to the block contents, but may also be indicated in others ways: by boxing the contents, by changing the font or size of the nested text, or even by folding the text (so long as a visible placeholder is provided).
Occasionally it is desirable to nest content by more than one level:
=begin para :nested
=begin para :nested
=begin para :nested
"We're going deep, deep, I<deep> undercover!"
=end para
=end para
=end para
This can be simplified by giving the :nested option a positive integer value:
You can also give the option a value of zero, to defeat any implicit nesting that might normally be applied to a paragraph. For example, to specify a block of code that should appear without its usual nesting:
1 2 3 4 5 6
123456789012345678901234567890123456789012345678901234567890
|------|-----------------------|---------------------------|
line instruction comments
number code
=end code
Note that :!nested could also be used for this purpose:
=begin code :!nested
This option specifies that the block is to be numbered. The most common use of this option is to create numbered headings and ordered lists, but it can be applied to any block.
It is up to individual renderers to decide how to display any numbering associated with other types of blocks.
This option specifies that the contents of the block should be treated as if they had one or more formatting codes placed around them.
For example, instead of:
=for comment
The next para is both important and fundamental,
so doubly emphasize it...
=begin para
B<I<
Warning: Do not immerse in water. Do not expose to bright light.
Do not feed after midnight.
>>
=end para
you can just write:
The internal representations of these two versions are exactly the same, except that the second one retains the :formatted option information as part of the resulting block object.
Like all formatting codes, codes applied via a :formatted are inherently cumulative. For example, if the block itself is already inside a formatting code, that formatting code will still apply, in addition to the extra "basis" and "important" formatting specified by :formatted<B I>. =end item
=config head2 :like<head1> :formatted<I>
Pod offers notations for specifying a range of standard block types...
Pod provides an unlimited number of levels of heading, specified by the =headN block marker. For example:
=head1 A Top Level Heading
=head2 A Second Level Heading
=head3 A third level heading
=head86 A "Missed it by I<that> much!" heading
While Pod parsers are required to recognize and distinguish all levels of heading, Pod renderers are only required to provide distinct renderings of the first four levels of heading (though they may, of course, provide more than that). Headings at levels without distinct renderings would typically be rendered like the lowest distinctly rendered level.
You can specify that a heading is numbered using the :numbered option. For example:
=for head1 :numbered
The Problem
=for head1 :numbered
The Solution
=for head2 :numbered
Analysis
=for head3
Overview
=for head3
Details
=for head2 :numbered
Design
=for head1 :numbered
The Implementation
which would produce:
2. The Solution
Details =end nested
2.2: Design =end nested
3. The Implementation =end nested
It is usually better to preset a numbering scheme for each heading level, in a series of configuration blocks:
=head1 The Problem
=head1 The Solution
=head2 Analysis
=head3 Overview
=head3 Details
=head2 Design
=head1 The Implementation
Alternatively, as a short-hand, if the first whitespace-delimited word in a heading consists of a single literal # character, the # is removed and the heading is treated as if it had a :numbered option:
=head1 # The Problem
=head1 # The Solution
=head2 # Analysis
=head3 Overview
=head3 Details
=head2 # Design
=head1 # The Implementation
Note that, even though renderers are not required to distinctly render more than the first four levels of heading, they are required to correctly honour arbitrarily nested numberings. That is:
=head6 # The Rescue of the Kobayashi Maru
should produce something like:
Ordinary paragraph blocks consist of text that is to be formatted into a document at the current level of nesting, with whitespace squeezed, lines filled, and any special inline mark-up applied.
Ordinary paragraphs consist of one or more consecutive lines of text, each of which starts with a non-whitespace character at column 1. The paragraph is terminated by the first blank line or block directive. For example:
=head1 This is a heading block
This is an ordinary paragraph.
Its text will be squeezed and
short lines filled. It is terminated by
the first blank line.
This is another ordinary paragraph.
Its text will also be squeezed and
short lines filled. It is terminated by
the trailing directive on the next line.
=head2 This is another heading block
Within a =pod, =item, =nested, =END, or semantic block, ordinary paragraphs do not require an explicit marker or delimiters, but there is also an explicit para marker (which may be used anywhere):
and likewise the longer =for and =begin/=end forms. For example:
This is I<still> part of the same paragraph,
which continues until an...
B<=end para>
=end code
As the previous example implies, when any form of explicit para block is used, any whitespace at the start of each line is removed, so the paragraph text no longer has to begin at column 1. In addition, within a delimited =begin para/=end para block, any blank lines are preserved.
Code blocks are used to specify pre-formatted text (typically source code), which should be rendered without rejustification, without whitespace-squeezing, and without recognizing any inline formatting codes. Code blocks also have an implicit nesting associated with them. Typically these blocks are used to show examples of code, mark-up, or other textual specifications, and are rendered using a fixed-width font.
A code block may be implicitly specified as one or more lines of text, each of which starts with a whitespace character. The block is terminated by a blank line. For example:
$this = 1 * code('block');
$which.is_specified(:by<indenting>);
=end code
Implicit code blocks may only be used within =pod, =item, =nested, =END, or semantic blocks.
There is also an explicit =code block (which can be specified within any other block type, not just =pod, =item, etc.):
B<=begin code>
sub loud_update ($who, $status) {
say "$who -> $status";
silent_update($who, $status);
}
B<=end code>
=end code
As the previous example demonstrates, within an explicit =code block the code can start at the first column. Furthermore, lines that start with whitespace characters have that whitespace preserved exactly (in addition to the implicit nesting of the code). Explicit =code blocks may also contain empty lines.
Although =code blocks automatically disregard all formatting codes, occasionally you may still need to specify some formatting within a code block. For example, you may wish to emphasize a particular keyword in an example (using a code). Or you may want to indicate that part of the example is metasyntactic (using the code). Or you might need to insert a non-ASCII character (using the E<> code).
You can specify a list of formatting codes that should still be recognized within a code block using the :allow option. The value of the :allow option must be a list of the (single-letter) names of one or more formatting codes. Those codes will then remain active inside the code block. For example:
=begin code :allow< B R >
sub demo {
B<say> 'Hello R<name>';
}
=end code
would be rendered:
Although code blocks are verbatim by default, it can still occasionally be useful to explicitly :allow the verbatim formatting code (). That's because, although the contents of an explicit =code block are allowed to start in column 1, they are not allowed to start with an equals sign in that first columnBecause an = in the first column is always the start of a Pod directive. So, if an = is needed in column 1, it must be declared verbatim:
B<V<=>> in the first column is always a Perldoc directive
=end code
=end code
Pod also provides blocks for specifying the input and output of programs.
The =input block is used to specify pre-formatted keyboard input, which should be rendered without rejustification or squeezing of whitespace.
The =output block is used to specify pre-formatted terminal or file output which should also be rendered without rejustification or whitespace-squeezing.
Note that, like =code blocks, both =input and =output blocks have an implicit level of nesting. They are also like =code blocks in that they are typically rendered in a fixed-width font, though ideally all three blocks would be rendered in distinct font/weight combinations (for example: regular serifed for code, bold sans-serif for input, and regular sans-serif for output).
Unlike =code blocks, both =input and =output blocks honour any nested formatting codes. This is particularly useful since a sample of input will often include prompts (which are, of course, output). Likewise a sample of output may contain the occasional interactive component. Pod provides special formatting codes ( and ) to indicate embedded input or output, so you can use the block type that indicates the overall purpose of the sample (i.e. is it demonstrating an input operation or an output sequence?) and then use the "contrasting" formatting code within the block.
For example, to include a small amount of input in a sample of output:
Do you want additional personnel details? B<K<y>>
Height: 180cm/5'11"
Weight: 104kg/230lb
Age: 49
Print? B<K<n>>
=end output
=end code
Lists in Pod are specified as a series of contiguous =item blocks. No special "container" directives or other delimiters are required to enclose the entire list. For example:
The seven suspects are:
=item Happy
=item Dopey
=item Sleepy
=item Bashful
=item Sneezy
=item Grumpy
=item Keyser Soze
List items have one implicit level of nesting:
Lists may be multi-level, with items at each level specified using the =item1, =item2, =item3, etc. blocks. Note that =item is just an abbreviation for =item1. For example:
=item1 Animal
=item2 Vertebrate
=item2 Invertebrate
=item1 Phase
=item2 Solid
=item2 Liquid
=item2 Gas
=item2 Chocolate
which would be rendered something like:
Perldoc parsers must issue a warning if a "level-N+1" =item block (e.g. an =item2, =item3, etc.) appears anywhere except where there is a preceding "level-N" =item in the same surrounding block. That is, an =item3 should only be specified if an =item2 appears somewhere before it, and that =item2 should itself only appear if there is a preceding =item1.
Note that item blocks within the same list are not physically nested. That is, lower-level items should not be specified inside higher-level items:
=comment WRONG...
=begin item1 --------------
The choices are: |
=item2 Liberty ==< Level 2 |==< Level 1
=item2 Death ==< Level 2 |
=item2 Beer ==< Level 2 |
=end item1 --------------
=comment CORRECT...
=begin item1 ---------------
The choices are: |==< Level 1
=end item1 ---------------
=item2 Liberty ==================< Level 2
=item2 Death ==================< Level 2
=item2 Beer ==================< Level 2
An item is part of an ordered list if the item has a :numbered configuration option:
=for item1 :numbered
Visito
=for item2 :numbered
Veni
=for item2 :numbered
Vidi
=for item2 :numbered
Vici
This would produce something like:
1.2. Vidi
1.3. Vici =end nested =end nested
although the numbering scheme is entirely at the discretion of the renderer, so it might equally well be rendered:
1b. Vidi
1c. Vici =end nested =end nested
or even:
(ii) Vidi
(iii) Vici =end nested =end nested
Alternatively, if the first word of the item consists of a single # character, the item is treated as having a :numbered option:
=item1 # Visito
=item2 # Veni
=item2 # Vidi
=item2 # Vici
To specify an unnumbered list item that starts with a literal #, either make it verbatim:
or explicitly mark the item itself as being unnumbered:
The numbering of successive =item1 list items increments automatically, but is reset to 1 whenever any other kind of non-ambient Perldoc block appears between two =item1 blocks. For example:
The options are:
=item1 # Liberty
=item1 # Death
=item1 # Beer
The tools are:
=item1 # Revolution
=item1 # Deep-fried peanut butter sandwich
=item1 # Keg
would produce:
The tools are:
The numbering of nested items (=item2, =item3, etc.) only resets (to 1) when the higher-level item's numbering either resets or increments.
To prevent a numbered =item1 from resetting after a non-item block, you can specify the :continued option:
=for item1
# Learn the hidden mysteries of space and time
I<????>
=for item1 B<:continued>
# Prophet!
=end code
which produces:
To create term/definition lists, specify the term as a configuration value of the item, and the definition as the item's contents:
=for item B<:term<MEEKNESS>>
Uncommon patience in planning a revenge that is worth while.
=for item B<:term<MORAL>>
Conforming to a local and mutable standard of right.
Having the quality of general expediency.
=end code
An item that's specified as a term can still be numbered:
=for item B<:numbered> :term<SUCCESS>
The one unpardonable sin against one's fellows.
=end code
List items that do not specify either the :numbered or :term options are unordered. Typically, such lists are rendered with bullets. For example:
=item1 Reading
=item2 Writing
=item3 'Rithmetic
might be rendered:
As with numbering styles, the bulleting strategy used for different levels within a nested list is entirely up to the renderer.
Use the delimited form of the =item block to specify items that contain multiple paragraphs. For example:
Let's consider two common proverbs:
=begin item :numbered
I<The rain in Spain falls mainly on the plain.>
This is a common myth and an unconscionable slur on the Spanish
people, the majority of whom are extremely attractive.
=end item
=begin item :numbered
I<The early bird gets the worm.>
In deciding whether to become an early riser, it is worth
considering whether you would actually enjoy annelids
for breakfast.
=end item
As you can see, folk wisdom is often of dubious value.
which produces:
This is a common myth and an unconscionable slur on the Spanish people, the majority of whom are extremely attractive. =end item
In deciding whether to become an early riser, it is worth considering whether you would actually enjoy annelids for breakfast. =end item
As you can see, folk wisdom is often of dubious value. =end nested
Any block can be nested by specifying an :nested option on it:
However, qualifying each nested paragraph individually quickly becomes tedious if there are many in a sequence, or if multiple levels of nesting are required:
So Pod provides a =nested block that marks all its contents as being nested:
Nesting blocks can contain any other kind of block, including implicit paragraph and code blocks.
Simple tables can be specified in Perldoc using a =table block. The table may be given an associated description or title using the :caption option.
Columns are separated by whitespace, vertical lines (|), or border intersections (+). Rows can be specified in one of two ways: either one row per line, with no separators; or multiple lines per row with explicit horizontal separators (whitespace, intersections (+), or horizontal lines: -, =, _) between every row. Either style can also have an explicitly separated header row at the top.
Each individual table cell is separately formatted, as if it were a nested =para.
This means you can create tables compactly, line-by-line:
=table
The Shoveller Eddie Stevens King Arthur's singing shovel
Blue Raja Geoffrey Smith Master of cutlery
Mr Furious Roy Orson Ticking time bomb of fury
The Bowler Carol Pinnsler Haunted bowling ball
or line-by-line with multi-line headers:
=table
Superhero | Secret |
| Identity | Superpower
==============|=================|================================
The Shoveller | Eddie Stevens | King Arthur's singing shovel
Blue Raja | Geoffrey Smith | Master of cutlery
Mr Furious | Roy Orson | Ticking time bomb of fury
The Bowler | Carol Pinnsler | Haunted bowling ball
or with multi-line headers and multi-line data:
=begin table :caption('The Other Guys')
Secret
Superhero Identity Superpower
============= =============== ===================
The Shoveller Eddie Stevens King Arthur's
singing shovel
Blue Raja Geoffrey Smith Master of cutlery
Mr Furious Roy Orson Ticking time bomb
of fury
The Bowler Carol Pinnsler Haunted bowling ball
=end table
Blocks whose names are not recognized as Pod built-ins are assumed to be destined for specialized renderers or parser plug-ins. For example:
=begin Xhtml
<object type="video/quicktime" data="onion.mov">
=end Xhtml
or:
=Image http://www.perlfoundation.org/images/perl_logo_32x104.png
Named blocks are converted by the Perldoc parser to block objects; specifically, to objects of a subclass of the standard Perldoc::Block::Named class.
For example, the blocks of the previous example would be converted to objects of the classes Perldoc::Block::Named::Xhtml and Perldoc::Block::Named::Image respectively. Both of those classes would be automatically created as subclasses of the Perldoc::Block::Named class (unless they were already defined via a prior =use directive).
The resulting object's .typename method retrieves the short name of the block type: 'Xhtml', 'Image', etc. The object's .config method retreives the list of configuration options (if any). The object's .contents method retrieves a list of the block's verbatim contents.
Named blocks for which no explicit class has been defined or loaded are usually not rendered by the standard renderers.
Note that all block names consisting entirely of lower-case or entirely of upper-case letters are reserved. See "#Semantic blocks".
Comments are Pod blocks that are never rendered by any renderer. They are, of course, still included in any internal Perldoc representation, and are accessible via the Perldoc API.
Comments are useful for meta-documentation (documenting the documentation):
=comment Add more here about the algorithm
and for temporarily removing parts of a document:
=item # Learn the hidden mysteries of space and time
=item # Achieve enlightenment
B<=begin comment>
=item # Prophet!
B<=end comment>
=end code
Note that, since the Perl interpreter never executes embedded Perldoc blocks, comment blocks can also be used as (nestable!) block comments in Perl 6:
=begin comment
for my $file (@files) {
system("rm -rf $file");
}
=end comment
=END blockThe =END block is special in that all three of its forms (delimited, paragraph, and abbreviated) are terminated only by the end of the current file. That is, neither =END nor =for END are terminated by the next blank line, and =end END has no effect within a =begin END block. A warning is issued if an explicit =end END appears within a document.
An =END block indicates the end-point of any ambient material within the document. This means that the parser will treat all the remaining text in the file as Perldoc, even if it is not inside an explicit block. In other words, apart from its special end-of-file termination behaviour, an =END block is in all other respects identical to a =pod block.
Named Perldoc blocks whose typename is DATA are the Perl 6 equivalent of the Perl 5 __DATA__ section. The difference is that =DATA blocks are just regular Pod blocks and may appear anywhere within a source file, and as many times as required. Synopsis 2 describes the new Perl 6 interface for inline data.
All other uppercase block typenames are reserved for specifying standard documentation, publishing, or source components. In particular, all the standard components found in Perl and manpage documentation have reserved uppercase typenames.
Standard semantic blocks include:
=NAME
=VERSION
=SYNOPSIS
=DESCRIPTION
=USAGE
=INTERFACE
=METHOD
=SUBROUTINE
=OPTION
=DIAGNOSTIC
=ERROR
=WARNING
=DEPENDENCY
=BUG
=SEEALSO
=ACKNOWLEDGEMENT
=AUTHOR
=COPYRIGHT
=DISCLAIMER
=LICENCE
=LICENSE
=TITLE
=SECTION
=CHAPTER
=APPENDIX
=TOC
=INDEX
=FOREWORD
=SUMMARY
The plural forms of each of these keywords are also reserved, and are aliases for the singular forms.
Most of these blocks would typically be used in their full delimited forms:
my Perldoc::Parser $parser .= new();
my $tree = $parser.parse($fh);
=end SYNOPSIS
=end code
Semantic blocks can be considered to be variants of the =head1 block in most respects (and most renderers will treat them as such). The main difference is that, in a =head1 block, the heading is the contents of the block; whereas, in a semantic block, the heading is derived from the typename of the block itself and the block contents are instead treated as the =para or =code block(s) belonging to the heading.
The use of these special blocks is not required; you can still just write:
my Perldoc::Parser $parser .= new();
my $tree = $parser.parse($fh);
=end code
=end code
However, using the keywords adds semantic information to the documentation, which may assist various renderers, summarizers, coverage tools, document refactorers, and other utilities. This is because a semantic block encloses the text it controls (unlike a =head1, which merely precedes its corresponding text), so using semantic blocks produces a more explicitly structured document.
Note that there is no requirement that semantic blocks be rendered in a particular way (or at all). Specifically, it is not necessary to preserve the capitalization of the keyword. For example, the =SYNOPSIS block of the preceding example might be rendered like so:
my $rep = Perl6::Perldoc::Parser.parse($fh, :all_pod); =end code =end nested
Formatting codes provide a way to add inline mark-up to a piece of text within the contents of (most types of) block. Formatting codes are themselves a type of block, and most of them may nest sequences of any other type of block (most often, other formatting codes). In particular, you can nest comment blocks in the middle of a formatting code:
All Pod formatting codes consist of a single capital letter followed immediately by a set of angle brackets. The brackets contain the text or data to which the formatting code applies. You can use a set of single angles (C«<...>»), a set of double angles («...»), or multiple single-angles (C«<<<...>>>»).
Within angle delimiters, you cannot use sequences of the same angle characters that are longer than the delimiters:
C< $fooB«<<»barB«>>» >
The Perl 5 heredoc syntax was: C< B«<<»END_MARKER >
=end code
You can use sequences of angles that are the same length as the delimiters, but they must be balanced. For example:
C< $foo<bar> >
C<< $foo<<bar>> >>
If you need an unbalanced angle, either use different delimiters:
or delimiters with more consecutive angles than your text contains:
A formatting code ends at the matching closing angle bracket(s), or at the end of the enclosing block or formatting code in which the opening angle bracket was specified, whichever comes first. Pod parsers are required to issue a warning whenever a formatting code is terminated by the end of an outer block rather than by its own delimiter (unless the user explicitly disables the warning).
Pod provides three formatting codes that flag their contents with increasing levels of significance:
<em...<em/> > tags
<strong...</strong> > tags.The formatting code indicates that the contained text is a definition, introducing a term that the adjacent text elucidates. For example:
A definition may be given synonyms, which are specified after a vertical bar and separated by semicolons:
A definition would typically be rendered in italics or <dfn...</dfn> > tags and will often be used as a link target for subsequent instances of the term (or any of its specified synonyms) within a hypertext.
Perldoc provides formatting codes for specifying inline examples of input, output, code, and metasyntax:
To include other formatting codes in a
To enable entities in every ...=config > at the top of the document =end item :allow<E
or:
=for input
Name: B<R<your surname>>
ID: B<R<your employee number>>
Pass: B<R<your 36-letter password>>
=end code
Typically replaceables would be rendered in fixed-width italics or with <var...</var> > tags. The font used should be the same as that used for the is inside a or code (or the equivalent =input or =output blocks), in which case their respective fonts should be used. =end item
The formatting code treats its entire contents as being verbatim, disregarding every apparent formatting code within it. For example:
The B<V< V<> >> formatting code disarms other codes
such as V< I<>, C<>, B<>, and M<> >.
Note, however that the code only changes the way its contents are parsed, not the way they are rendered. That is, the contents are still wrapped and formatted like plain text, and the effects of any formatting codes surrounding the code are still applied to its contents. For example the previous example is rendered:
You can prespecify formatting codes that remain active within a code, using the :allow option.
The formatting code indicates that its contents constitute a zero-width comment, which should not be rendered by any renderer. For example:
In Perl 5 POD, the code was widely used to break up text that would otherwise be considered mark-up:
That technique still works, but it's now easier to accomplish the same goal using a verbatim formatting code:
Moreover, the as well:
The formatting code is the inline equivalent of a =comment block.
The L<> code is used to specify all kinds of links, filenames, citations, and cross-references (both internal and external).
A link specification consists of a scheme specifier terminated by a colon, followed by an external address (in the scheme's preferred syntax), followed by an internal address (again, in the scheme's syntax). All three components are optional, though at least one must be present in any link specification.
Usually, in schemes where an internal address makes sense, it will be separated from the preceding external address by a #, unless the particular addressing scheme requires some other syntax. When new addressing schemes are created specifically for Perldoc it is strongly recommended that # be used to mark the start of internal addresses.
Standard schemes include:
If the link does not start with // it is treated as being relative to the location of the current document:
A filename on the local system. For example:
Filenames that don't begin with a / or a ~ are relative to the current document's location:
An email address. Typically, activating this type of link invokes a mailer. For example:
A link to the system manpages. For example:
A link to some other documentation, typically a module or part of the core documentation. For example:
A link to the definition of the specified term within the current document. For example:
and later, to link back to the definition
The International Standard Book Number or International Standard Serial Number for a publication. For example:
To refer to a specific section within a webpage, manpage, or Perldoc document, add the name of that section after the main link, separated by a #. For example:
To refer to a section of the current document, omit the external address:
The scheme name may also be omitted in that case:
Normally a link is presented as some rendered version of the link specification itself. However, you can specify an alternate presentation by prefixing the link with the desired text and a vertical bar. Whitespace is not significant on either side of the bar. For example:
You could also write the code
L<B<in Latin |> doc:Lingua::Romana::Perligata>
=end code
A second kind of link—the or placement link—works in the opposite direction. Instead of directing focus out to another document, it allows you to draw the contents of another document into your own.
In other words, the formatting code takes a URI and (where possible) places the contents of the corresponding document inline in place of the code itself.
codes are handy for breaking out standard elements of your documentation set into reusable components that can then be incorporated directly into multiple documents. For example:
=COPYRIGHT
P<file:/shared/docs/std_copyright.pod>
=DISCLAIMER
P<http://www.MegaGigaTeraPetaCorp.com/std/disclaimer.txt>
might produce:
This document is copyright (c) MegaGigaTeraPetaCorp, 2006. All rights reserved.
Disclaimer
ABSOLUTELY NO WARRANTY IS IMPLIED. NOT EVEN OF ANY KIND. WE HAVE SOLD YOU THIS SOFTWARE WITH NO HINT OF A SUGGESTION THAT IT IS EITHER USEFUL OR USABLE. AS FOR GUARANTEES OF CORRECTNESS...DON'T MAKE US LAUGH! AT SOME TIME IN THE FUTURE WE MIGHT DEIGN TO SELL YOU UPGRADES THAT PURPORT TO ADDRESS SOME OF THE APPLICATION'S MANY DEFICIENCIES, BUT NO PROMISES THERE EITHER. WE HAVE MORE LAWYERS ON STAFF THAN YOU HAVE TOTAL EMPLOYEES, SO DON'T EVEN *THINK* ABOUT SUING US. HAVE A NICE DAY. =end nested
If a renderer cannot find or access the external data source for a placement link, it must issue a warning and render the URI directly in some form, possibly as an outwards link. For example:
See: std_copyright.pod
Disclaimer
See: http://www.MegaGigaTeraPetaCorp.com/std/disclaimer.txt =end nested
You can use any of the following URI forms (see #Links) in a placement link:
http: and https: =item file: =item man: =item doc: =item toc:The toc: form is a special pseudo-scheme that inserts a table of contents in place of the code. After the colon, list the block types that you wish to include in the table of contents. For example, to place a table of contents listing only top- and second-level headings:
P<toc: head1 head2>
To place a table of contents that lists the top four levels of headings, as well as any tables:
P<toc: head1 head2 head3 head4 table>
To place a table of diagrams (assuming a user-defined Diagram block):
P<toc: Diagram>
Note also that, for toc:..., all semantic blocks are treated as equivalent to head1 headings, and the =item1/=item equivalence is preserved.
Any text enclosed in an code is formatted normally, except that every whitespace character in it—including any newline—is preserved. These characters are also treated as being non-breaking (except for the newlines, of course). For example:
The emergency signal is: S<
dot dot dot dash dash dash dot dot dot>.
would be formatted like so:
rather than:
To include named Unicode or XHTML entities, use the E<> code.
If the contents of the E<> are a number, that number is treated as the decimal Unicode value for the desired codepoint. For example:
Perl 6 makes considerable use of E<171> and E<187>.
You can also use explicit binary, octal, decimal, or hexadecimal numbers (using the Perl 6 notations for explicitly based numbers):
Perl 6 makes considerable use of E<0b10101011> and E<0b10111011>.
Perl 6 makes considerable use of E<0o253> and E<0o273>.
Perl 6 makes considerable use of E<0d171> and E<0d187>.
Perl 6 makes considerable use of E<0xAB> and E<0xBB>.
If the contents are not a number, they are interpreted as a Unicode character name (which is always upper-case), or else as an XHTML entity. For example:
Perl 6 makes considerable use of E<LEFT DOUBLE ANGLE BRACKET>
and E<RIGHT DOUBLE ANGLE BRACKET>.
or, equivalently:
Perl 6 makes considerable use of E<laquo> and E<raquo>.
Multiple consecutive entities can be specified in a single E<> code, separated by semicolons:
Perl 6 makes considerable use of E<laquo;hellip;raquo>.
Anything enclosed in an code is an index entry. The contents of the code are both formatted into the document and used as the (case-insensitive) index entry:
You can specify an index entry in which the indexed text and the index entry are different, by separating the two with a vertical bar:
In the two-part form, the index entry comes after the bar and is case-sensitive.
You can specify hierarchical index entries by separating indexing levels with commas:
You can specify two or more entries for a single indexed text, by separating the entries with semicolons:
The indexed text can be empty, creating a "zero-width" index entry:
Anything enclosed in an code is an inline note. For example:
Renderers may render such annotations in a variety of ways: as footnotes, as endnotes, as sidebars, as pop-ups, as tooltips, as expandable tags, etc. They are never, however, rendered as unmarked inline text. So the previous example might be rendered as:
and later:
Perldoc modules can define their own formatting codes, using the code. An code must start with a colon-terminated scheme specifier. The rest of the enclosed text is treated as the (verbatim) contents of the formatting code. For example:
=head1 Overview of the B<M<TT: $CLASSNAME >> class
(version B<M<TT: $VERSION>>)
B<M<TT: get_description($CLASSNAME) >>
=end code
The formatting code is the inline equivalent of a named block.
Internally an code is converted to an object derived from the Perldoc::FormattingCode::Named class. The name of the scheme becomes the final component of the object's classname. For instance, the code in the previous example would be converted to a Perldoc::FormattingCode::Named::TT object, whose .typename method retrieves the string "TT" and whose .contents method retrieves a list of the formatting code's (verbatim, unformatted) contents.
If the formatting code is unrecognized, the contents of the code (i.e. everything after the first colon) would normally be rendered as ordinary text.
By default, Perldoc assumes that documents are Unicode, encoded in one of the three common schemes (UTF-8, UTF-16, or UTF-32). The particular scheme a document uses is autodiscovered by examination of the first few bytes of the file (where possible). If the autodiscovery fails, UTF-8 is assumed, and parsers may treat any non-UTF-8 bytes later in the document as fatal errors.
At any point in a document, you can explicitly set or change the encoding of its content using the =encoding directive:
=encoding ShiftJIS
=encoding Macintosh
=encoding KOI8-R
The specified encoding is used from the start of the next line in the document. If a second =encoding directive is encountered, the current encoding changes again after that line. Note, however, that the second encoding directive must itself be encoded using the first encoding scheme.
This requirement also applies to an =encoding directive at the very beginning of the file. That is, it must itself be encoded in the default UTF-8, -16, or -32. However, as a special case, the autodiscovery mechanism will (as far as possible) also attempt to recognize "self-encoded" =encoding directives that begin at the first byte of the file. For example, at the start of a ShiftJIS-encoded file you can specify =encoding ShiftJIS in the ShiftJIS encoding.
An =encoding directive affects any ambient code between the Perldoc as well. That is, Perl 6 uses =encoding directives to determine the encoding of its source code as well as that of any documentation.
Note that =encoding is a fundamental Perldoc directive, like =begin or =for; it is not an instance of an abbreviated block. Hence there is no paragraph or delimited form of the =encoding directive (just as there is no paragraph or delimited form of =begin).
The =config directive allows you to prespecify standard configuration information that is applied to every block of a particular type.
For example, to specify particular formatting for different levels of heading, you could preconfigure all the heading directives with appropriate formatting schemes:
=config head1 :formatted<B U> :numbered
=config head2 :like<head1> :formatted<I>
=config head3 :formatted<U>
=config head4 :like<head3> :formatted<I>
The general syntax for configuration directives is:
Like =encoding, a =config is a directive, not a block. Hence, there is no paragraph or delimited form of the =config directive. Each =config specification is lexically scoped to the surrounding block in which it is specified.
Note that, if a particular block later explicitly specifies a configuration option with the same key, that option overrides the pre-configured option. For example, given the heading configurations in the previous example, to specify a non-basic second-level heading:
=for head2 :formatted<I U>
Details
The :like option causes the current formatting options for the named block type to be (lexically) replaced by the complete formatting information of the block type specified as the :like's value. That other block type must already have been preconfigured. Any additional formatting specifications are subsequently added to that config. For example:
Incidentally, this also means you can arrange for an explicit :formatted option to augment an existing =config, rather than replacing it. Like so:
You can also lexically preconfigure a formatting code, by naming it with a pair of angles as a suffix. For example:
Note that, even though the formatting code is named using single-angles, the preconfiguration applies regardless of the actual delimiters used on subsequent instances of the code.
Perldoc provides a mechanism by which you can extend the syntax, semantics, or content of your documentation: the =use directive.
Specifying a =use causes a Perldoc processor to load the corresponding Perldoc module at that point, or to throw an exception if it cannot.
Such modules can specify additional content that should be included in the document. Alternatively, they can register classes that handle new types of block directives or formatting codes.
Note that a module loaded via a =use statement can affect the content or the interpretation of subsequent blocks, but not the initial parsing of those blocks. Any new block types must still conform to the general syntax described in this document. Typically, a module will change the way that renderers parse the contents of specific blocks.
A =use directive may be specified with either a module name or a URI:
If a URI is given, the specified file is treated as a source of Pod to be included in the document. Any Pod blocks are parsed out of the contents of the =use'd file, and added to the main file's Pod representation at that point.
If a module name is specified, with a language prefix of pod:, then the corresponding .pod file is searched for in the $PERL6DOC "documentation path". If none is found, the corresponding .pm file is then searched for in the library path ($PERL6LIB). If either file is found, the Pod is parsed out of it and the resulting block objects inserted into the main file's representation.
If a module name is specified with any prefix except pod:, or without a prefix at all, then the corresponding .pm file (or another language's equivalent code module) is searched for in the appropriate module library path. If found, the code module require'd into the Pod parser (usually to add a class implementing a particular Pod extension). If no such code module is found, a suitable .pod file is searched for instead, the contents parsed as Pod, and the resulting block objects inserted into the main file's representation.
You can use fully and partially specified module names (as with Perl 6 modules):
=use Perldoc::Plugin::XHTML-1.2.1-(*)
Any options that are specified after the module name:
=use Perldoc::Plugin::Image :Jpeg prefix=>'http://dev.perl.org'
are passed to the internal require that loads the corresponding module.
Collectively these alternatives allow you to create standard documentation inserts or stylesheets, to include Pod extracted from other code files, or to specify new types of documentation blocks and formatting codes:
Note that =use is a fundamental Perldoc directive, like =begin or =encoding, so there is no paragraph or delimited form of =use.
Directive Specifies
_________ ____________________________________________________
C<=begin> Start of an explicitly terminated block
C<=config> Lexical modifications to a block or formatting code
C<=encoding> Encoding scheme for subsequent text
C<=end> Explicit termination of a C<=begin> block
C<=for> Start of an implicitly (blank-line) terminated block
C<=use> Transclusion of content; loading of a Perldoc module
Block typename Specifies
______________ ___________________________________________________
C<=code> Verbatim pre-formatted sample source code
C<=comment> Content to be ignored by all renderers
C<=head>R<N> I<N>th-level heading
C<=input> Pre-formatted sample input
C<=item> First-level list item
C<=item>R<N> I<N>th-level list item
C<=nested> Nest block contents within the current context
C<=output> Pre-formatted sample output
C<=para> Ordinary paragraph
C<=table> Simple rectangular table
C<=DATA> Perl 6 data section
C<=END> No ambient blocks after this point
C<=>R<RESERVED> Semantic blocks (C<=SYNOPIS>, C<=BUGS>, etc.)
C<=>R<Typename> User-defined block
Formatting code Specifies
_______________ ___________________________________________________
C<B<...>> Basis/focus of sentence (typically rendered bold)
C<C<...>> Code (typically rendered fixed-width)
C<D<...|...;...>> Definition (C<D<R<defined term>|R<synonym>;R<synonym>;...>>)
C<E<...>> Entity name or numeric codepoint
C<I<...>> Important (typically rendered in italics)
C<K<...>> Keyboard input (typically rendered fixed-width)
C<L<...|...>> Link (C<L<R<display text>|R<destination URI>>>)
C<M<...:...>> Module-defined code (C<M<R<scheme>:R<contents>>>)
C<N<...>> Note (not rendered inline)
C<P<...>> Placement link
C<V<R><...>> Replaceable component or metasyntax
C<S<...>> Space characters to be preserved
C<T<...>> Terminal output (typically rendered fixed-width)
C<U<...>> Unusual (typically rendered with underlining)
C<V<V><...>> Verbatim (internal formatting codes ignored)
C<X<...|..,..;...>> Index entry (C<X<R<display text>|R<entry>,R<subentry>;...>>)
C<Z<...>> Zero-width comment (contents never rendered)
