pod::parser(3)

NAME

Pod::Parser - base class for creating POD filters and
translators

SYNOPSIS

use Pod::Parser;
package MyParser;
@ISA = qw(Pod::Parser);
sub command {
    my ($parser, $command,  $paragraph,  $line_num)  =
@_;
    ##  Interpret the command and its text; sample actions might be:
    if ($command eq 'head1') { ... }
    elsif ($command eq 'head2') { ... }
    ## ... other commands and their actions
    my $out_fh = $parser->output_handle();
    my $expansion  =  $parser->interpolate($paragraph,
$line_num);
    print $out_fh $expansion;
}
sub verbatim {
    my ($parser, $paragraph, $line_num) = @_;
    ## Format verbatim paragraph; sample actions might
be:
    my $out_fh = $parser->output_handle();
    print $out_fh $paragraph;
}
sub textblock {
    my ($parser, $paragraph, $line_num) = @_;
    ## Translate/Format this block of text; sample actions might be:
    my $out_fh = $parser->output_handle();
    my  $expansion  = $parser->interpolate($paragraph,
$line_num);
    print $out_fh $expansion;
}
sub interior_sequence {
    my ($parser, $seq_command, $seq_argument) = @_;
    ## Expand an  interior  sequence;  sample  actions
might be:
    return  "*$seq_argument*"      if ($seq_command eq
'B');
    return "`$seq_argument'"     if  ($seq_command  eq
'C');
    return  "_${seq_argument}_'"   if ($seq_command eq
'I');
    ## ... other sequence commands and their resulting
text
}
package main;
## Create a parser object and have it parse file whose
name was
## given on the command-line (use STDIN  if  no  files
were given).
$parser = new MyParser();
$parser->parse_from_filehandle(TDIN)  if (@ARGV == 0);
for (@ARGV) { $parser->parse_from_file($_); }

REQUIRES

perl5.005, Pod::InputObjects, Exporter, Symbol, Carp

EXPORTS

Nothing.

DESCRIPTION

Pod::Parser is a base class for creating POD filters and translators. It handles most of the effort involved with
parsing the POD sections from an input stream, leaving
subclasses free to be concerned only with performing the
actual translation of text.

Pod::Parser parses PODs, and makes method calls to handle the various components of the POD. Subclasses of
Pod::Parser override these methods to translate the POD into whatever output format they desire.

QUICK OVERVIEW

To create a POD filter for translating POD documentation
into some other format, you create a subclass of
Pod::Parser which typically overrides just the base class implementation for the following methods:

· ccoommmmaanndd(())

· vveerrbbaattiimm(())

· tteexxttbblloocckk(())

· iinntteerriioorr__sseeqquueennccee(())

You may also want to override the bbeeggiinn__iinnppuutt(()) and eenndd__iinnppuutt(()) methods for your subclass (to perform any needed per-file and/or per-document initialization or
cleanup).

If you need to perform any preprocesssing of input before
it is parsed you may want to override one or more of pprree_
pprroocceessss__lliinnee(()) and/or pprreepprroocceessss__ppaarraaggrraapphh(()).

Sometimes it may be necessary to make more than one pass
over the input files. If this is the case you have several
options. You can make the first pass using Pod::Parser and override your methods to store the intermediate results in
memory somewhere for the eenndd__ppoodd(()) method to process. You could use Pod::Parser for several passes with an appropri ate state variable to control the operation for each pass.
If your input source can't be reset to start at the begin
ning, you can store it in some other structure as a string
or an array and have that structure implement a ggeettlliinnee(()) method (which is all that ppaarrssee__ffrroomm__ffiilleehhaannddllee(()) uses to read input).

Feel free to add any member data fields you need to keep
track of things like current font, indentation, horizontal
or vertical position, or whatever else you like. Be sure
to read "PRIVATE METHODS AND DATA" to avoid name colli
sions.

For the most part, the Pod::Parser base class should be able to do most of the input parsing for you and leave you
free to worry about how to intepret the commands and
translate the result.

Note that all we have described here in this quick
overview is the simplest most straightforward use of
Pod::Parser to do stream-based parsing. It is also possi ble to use the Pod::Parser::parse_text function to do more sophisticated tree-based parsing. See "TREE-BASED PARS
ING".

PARSING OPTIONS

A parse-option is simply a named option of Pod::Parser with a value that corresponds to a certain specified
behavior. These various behaviors of Pod::Parser may be enabled/disabled by setting or unsetting one or more
parse-options using the ppaarrsseeooppttss(()) method. The set of currently accepted parse-options is as follows:

-want_nonPODs (default: unset)

Normally (by default) Pod::Parser will only provide access to the POD sections of the input. Input para
graphs that are not part of the POD-format documenta
tion are not made available to the caller (not even
using pprreepprroocceessss__ppaarraaggrraapphh(())). Setting this option to a non-empty, non-zero value will allow pprreepprroocceessss__ppaarraa_ ggrraapphh(()) to see non-POD sections of the input as well as POD sections. The ccuuttttiinngg(()) method can be used to determine if the corresponding paragraph is a POD para
graph, or some other input paragraph.

-process_cut_cmd (default: unset)

Normally (by default) Pod::Parser handles the "=cut" POD directive by itself and does not pass it on to the
caller for processing. Setting this option to a
non-empty, non-zero value will cause Pod::Parser to pass the "=cut" directive to the caller just like any
other POD command (and hence it may be processed by the
ccoommmmaanndd(()) method).

Pod::Parser will still interpret the "=cut" directive to mean that "cutting mode" has been (re)entered, but
the caller will get a chance to capture the actual
"=cut" paragraph itself for whatever purpose it
desires.

-warnings (default: unset)

Normally (by default) Pod::Parser recognizes a bare minimum of pod syntax errors and warnings and issues
diagnostic messages for errors, but not for warnings.
(Use Pod::Checker to do more thorough checking of POD syntax.) Setting this option to a non-empty, non-zero
value will cause Pod::Parser to issue diagnostics for the few warnings it recognizes as well as the errors.

Please see "parseopts()" for a complete description of the interface for the setting and unsetting of parse-options.

RECOMMENDED SUBROUTINE/METHOD OVERRIDES

Pod::Parser provides several methods which most subclasses will probably want to override. These methods are as fol
lows:

ccoommmmaanndd(())

$parser->com

mand($cmd,$text,$line_num,$pod_para);

This method should be overridden by subclasses to take the
appropriate action when a POD command paragraph (denoted
by a line beginning with "=") is encountered. When such a
POD directive is seen in the input, this method is called
and is passed:

$cmd

the name of the command for this POD paragraph

$text

the paragraph text for the given POD paragraph command.

$line_num

the line-number of the beginning of the paragraph

$pod_para

a reference to a "Pod::Paragraph" object which contains
further information about the paragraph command (see
Pod::InputObjects for details).

Note that this method is called for "=pod" paragraphs.

The base class implementation of this method simply treats
the raw POD command as normal block of paragraph text
(invoking the tteexxttbblloocckk(()) method with the command para graph).

vveerrbbaattiimm(())

$parser->verbatim($text,$line_num,$pod_para);

This method may be overridden by subclasses to take the
appropriate action when a block of verbatim text is
encountered. It is passed the following parameters:

$text

the block of text for the verbatim paragraph

$line_num

the line-number of the beginning of the paragraph

$pod_para

a reference to a "Pod::Paragraph" object which contains
further information about the paragraph (see
Pod::InputObjects for details).

The base class implementation of this method simply prints
the textblock (unmodified) to the output filehandle.

tteexxttbblloocckk(())

$parser->textblock($text,$line_num,$pod_para);

This method may be overridden by subclasses to take the
appropriate action when a normal block of POD text is
encountered (although the base class method will usually
do what you want). It is passed the following parameters:

$text

the block of text for the a POD paragraph

$line_num

the line-number of the beginning of the paragraph

$pod_para

a reference to a "Pod::Paragraph" object which contains
further information about the paragraph (see
Pod::InputObjects for details).

In order to process interior sequences, subclasses imple
mentations of this method will probably want to invoke
either iinntteerrppoollaattee(()) or ppaarrssee__tteexxtt(()), passing it the text block $text, and the corresponding line number in
$line_num, and then perform any desired processing upon
the returned result.

The base class implementation of this method simply prints
the text block as it occurred in the input stream).

iinntteerriioorr__sseeqquueennccee(())

$parser->interior_se

quence($seq_cmd,$seq_arg,$pod_seq);

This method should be overridden by subclasses to take the
appropriate action when an interior sequence is encoun
tered. An interior sequence is an embedded command within
a block of text which appears as a command name (usually a
single uppercase character) followed immediately by a
string of text which is enclosed in angle brackets. This
method is passed the sequence command $seq_cmd and the
corresponding text $seq_arg. It is invoked by the iinntteerrppoo_ llaattee(()) method for each interior sequence that occurs in the string that it is passed. It should return the desired
text string to be used in place of the interior sequence.
The $pod_seq argument is a reference to a "Pod::Interi
orSequence" object which contains further information
about the interior sequence. Please see Pod::InputObjects
for details if you need to access this additional informa
tion.

Subclass implementations of this method may wish to invoke
the nneesstteedd(()) method of $pod_seq to see if it is nested inside some other interior-sequence (and if so, which
kind).

The base class implementation of the iinntteerriioorr__sseeqquueennccee(()) method simply returns the raw text of the interior
sequence (as it occurred in the input) to the caller.

OPTIONAL SUBROUTINE/METHOD OVERRIDES

Pod::Parser provides several methods which subclasses may want to override to perform any special pre/post-process
ing. These methods do not have to be overridden, but it
may be useful for subclasses to take advantage of them.

nneeww(())

my $parser = Pod::Parser->new();

This is the constructor for Pod::Parser and its sub classes. You do not need to override this method! It is
capable of constructing subclass objects as well as base
class objects, provided you use any of the following con
structor invocation styles:

my $parser1 = MyParser->new();
my $parser2 = new MyParser();
my $parser3 = $parser2->new();

where "MyParser" is some subclass of Pod::Parser.

Using the syntax "MyParser::new()" to invoke the construc
tor is not recommended, but if you insist on being able to
do this, then the subclass will need to override the nneeww(()) constructor method. If you do override the constructor,
you must be sure to invoke the iinniittiiaalliizzee(()) method of the newly blessed object.

Using any of the above invocations, the first argument to
the constructor is always the corresponding package name
(or object reference). No other arguments are required,
but if desired, an associative array (or hash-table) my be
passed to the nneeww(()) constructor, as in:

my $parser1 = MyParser->new( MYDATA => $value1, MORE

DATA => $value2 );
my $parser2 = new MyParser( -myflag => 1 );

All arguments passed to the nneeww(()) constructor will be treated as key/value pairs in a hash-table. The newly con
structed object will be initialized by copying the
contents of the given hash-table (which may have been
empty). The nneeww(()) constructor for this class and all of its subclasses returns a blessed reference to the initial
ized object (hash-table).

iinniittiiaalliizzee(())

$parser->initialize();

This method performs any necessary object initialization.
It takes no arguments (other than the object instance of
course, which is typically copied to a local variable
named $self). If subclasses override this method then they
must be sure to invoke "$self->SUPER::initialize()".

bbeeggiinn__ppoodd(())

$parser->begin_pod();

This method is invoked at the beginning of processing for
each POD document that is encountered in the input. Sub
classes should override this method to perform any perdocument initialization.

bbeeggiinn__iinnppuutt(())

$parser->begin_input();

This method is invoked by ppaarrssee__ffrroomm__ffiilleehhaannddllee(()) immedi ately before processing input from a filehandle. The base
class implementation does nothing, however, subclasses may
override it to perform any per-file initializations.

Note that if multiple files are parsed for a single POD
document (perhaps the result of some future "=include"
directive) this method is invoked for every file that is
parsed. If you wish to perform certain initializations
once per document, then you should use bbeeggiinn__ppoodd(()).

eenndd__iinnppuutt(())

$parser->end_input();

This method is invoked by ppaarrssee__ffrroomm__ffiilleehhaannddllee(()) immedi ately after processing input from a filehandle. The base
class implementation does nothing, however, subclasses may
override it to perform any per-file cleanup actions.

Please note that if multiple files are parsed for a single
POD document (perhaps the result of some kind of
"=include" directive) this method is invoked for every
file that is parsed. If you wish to perform certain
cleanup actions once per document, then you should use
eenndd__ppoodd(()).

eenndd__ppoodd(())

$parser->end_pod();

This method is invoked at the end of processing for each
POD document that is encountered in the input. Subclasses
should override this method to perform any per-document
finalization.

pprreepprroocceessss__lliinnee(())

$textline = $parser->preprocess_line($text,

$line_num);

This method should be overridden by subclasses that wish
to perform any kind of preprocessing for each line of
input (before it has been determined whether or not it is
part of a POD paragraph). The parameter $text is the input
line; and the parameter $line_num is the line number of
the corresponding text line.

The value returned should correspond to the new text to
use in its place. If the empty string or an undefined
value is returned then no further processing will be per
formed for this line.

Please note that the pprreepprroocceessss__lliinnee(()) method is invoked before the pprreepprroocceessss__ppaarraaggrraapphh(()) method. After all (pos sibly preprocessed) lines in a paragraph have been assem
bled together and it has been determined that the para
graph is part of the POD documentation from one of the
selected sections, then pprreepprroocceessss__ppaarraaggrraapphh(()) is invoked.

The base class implementation of this method returns the
given text.

pprreepprroocceessss__ppaarraaggrraapphh(())

$textblock = $parser->preprocess_para

graph($text, $line_num);

This method should be overridden by subclasses that wish
to perform any kind of preprocessing for each block (para
graph) of POD documentation that appears in the input
stream. The parameter $text is the POD paragraph from the
input file; and the parameter $line_num is the line number
for the beginning of the corresponding paragraph.

The value returned should correspond to the new text to
use in its place If the empty string is returned or an
undefined value is returned, then the given $text is
ignored (not processed).

This method is invoked after gathering up all the lines in
a paragraph and after determining the cutting state of the
paragraph, but before trying to further parse or interpret
them. After pprreepprroocceessss__ppaarraaggrraapphh(()) returns, the current cutting state (which is returned by "$self->cutting()") is
examined. If it evaluates to true then input text (includ
ing the given $text) is cut (not processed) until the next
POD directive is encountered.

Please note that the pprreepprroocceessss__lliinnee(()) method is invoked before the pprreepprroocceessss__ppaarraaggrraapphh(()) method. After all (pos sibly preprocessed) lines in a paragraph have been assem
bled together and either it has been determined that the
paragraph is part of the POD documentation from one of the
selected sections or the "-want_nonPODs" option is true,
then pprreepprroocceessss__ppaarraaggrraapphh(()) is invoked.

The base class implementation of this method returns the
given text.

METHODS FOR PARSING AND PROCESSING

Pod::Parser provides several methods to process input text. These methods typically won't need to be overridden
(and in some cases they can't be overridden), but sub
classes may want to invoke them to exploit their function
ality.

ppaarrssee__tteexxtt(())

$ptree1 = $parser->parse_text($text,

$line_num);
$ptree2 = $parser->parse_text({%opts}, $text,

$line_num);
$ptree3 = $parser->parse_text(opts, $text,

$line_num);

This method is useful if you need to perform your own
interpolation of interior sequences and can't rely upon
interpolate to expand them in simple bottom-up order.

The parameter $text is a string or block of text to be
parsed for interior sequences; and the parameter $line_num
is the line number curresponding to the beginning of
$text.

ppaarrssee__tteexxtt(()) will parse the given text into a parse-tree of "nodes." and interior-sequences. Each "node" in the
parse tree is either a text-string, or a Pod::InteriorSe quence. The result returned is a parse-tree of type
Pod::ParseTree. Please see Pod::InputObjects for more information about Pod::InteriorSequence and Pod::Parse Tree.

If desired, an optional hash-ref may be specified as the
first argument to customize certain aspects of the parsetree that is created and returned. The set of recognized
option keywords are:

-expand_seq => code-ref|method-name

Normally, the parse-tree returned by ppaarrssee__tteexxtt(()) will contain an unexpanded "Pod::InteriorSequence" object
for each interior-sequence encountered. Specifying
-expand_seq tells ppaarrssee__tteexxtt(()) to "expand" every inte rior-sequence it sees by invoking the referenced func
tion (or named method of the parser object) and using
the return value as the expanded result.

If a subroutine reference was given, it is invoked as:

&$code_ref( $parser, $sequence )

and if a method-name was given, it is invoked as:

$parser->method_name( $sequence )

where $parser is a reference to the parser object, and
$sequence is a reference to the interior-sequence
object. [NOTE: If the iinntteerriioorr__sseeqquueennccee(()) method is specified, then it is invoked according to the inter
face specified in "interior_sequence()"].

-expand_text => code-ref|method-name

Normally, the parse-tree returned by ppaarrssee__tteexxtt(()) will contain a text-string for each contiguous sequence of
characters outside of an interior-sequence. Specifying
-expand_text tells ppaarrssee__tteexxtt(()) to "preprocess" every such text-string it sees by invoking the referenced
function (or named method of the parser object) and
using the return value as the preprocessed (or
"expanded") result. [Note that if the result is an
interior-sequence, then it will not be expanded as
specified by the -expand_seq option; Any such recursive expansion needs to be handled by the specified callback
routine.]

If a subroutine reference was given, it is invoked as:

&$code_ref( $parser, $text, $ptree_node )

and if a method-name was given, it is invoked as:

$parser->method_name( $text, $ptree_node )

where $parser is a reference to the parser object,
$text is the text-string encountered, and $ptree_node
is a reference to the current node in the parse-tree
(usually an interior-sequence object or else the toplevel node of the parse-tree).

-expand_ptree => code-ref|method-name

Rather than returning a "Pod::ParseTree", pass the
parse-tree as an argument to the referenced subroutine
(or named method of the parser object) and return the
result instead of the parse-tree object.

If a subroutine reference was given, it is invoked as:

&$code_ref( $parser, $ptree )

and if a method-name was given, it is invoked as:

$parser->method_name( $ptree )

where $parser is a reference to the parser object, and
$ptree is a reference to the parse-tree object.

iinntteerrppoollaattee(())

$textblock = $parser->interpolate($text,

$line_num);

This method translates all text (including any embedded
interior sequences) in the given text string $text and
returns the interpolated result. The parameter $line_num
is the line number corresponding to the beginning of
$text.

iinntteerrppoollaattee(()) merely invokes a private method to recur sively expand nested interior sequences in bottom-up order
(innermost sequences are expanded first). If there is a
need to expand nested sequences in some alternate order,
use parse_text instead.

ppaarrssee__ffrroomm__ffiilleehhaannddllee(())

$parser->parse_from_filehan

dle($in_fh,$out_fh);

This method takes an input filehandle (which is assumed to
already be opened for reading) and reads the entire input
stream looking for blocks (paragraphs) of POD documenta
tion to be processed. If no first argument is given the
default input filehandle "STDIN" is used.

The $in_fh parameter may be any object that provides a
ggeettlliinnee(()) method to retrieve a single line of input text (hence, an appropriate wrapper object could be used to
parse PODs from a single string or an array of strings).

Using "$in_fh->getline()", input is read line-by-line and
assembled into paragraphs or "blocks" (which are separated
by lines containing nothing but whitespace). For each
block of POD documentation encountered it will invoke a
method to parse the given paragraph.

If a second argument is given then it should correspond to
a filehandle where output should be sent (otherwise the
default output filehandle is "STDOUT" if no output file
handle is currently in use).

NOTE: For performance reasons, this method caches the
input stream at the top of the stack in a local variable.
Any attempts by clients to change the stack contents
during processing when in the midst executing of this
method will not affect the input stream used by the cur rent invocation of this method.

This method does not usually need to be overridden by sub
classes.

ppaarrssee__ffrroomm__ffiillee(())

$parser->parse_from_file($filename,$outfile);

This method takes a filename and does the following:

· opens the input and output files for reading (creating

the appropriate filehandles)

· invokes the ppaarrssee__ffrroomm__ffiilleehhaannddllee(()) method passing it

the corresponding input and output filehandles.

· closes the input and output files.

If the special input filename "-" or "<&STDIN" is given
then the STDIN filehandle is used for input (and no open
or close is performed). If no input filename is specified
then "-" is implied.

If a second argument is given then it should be the name
of the desired output file. If the special output filename
"-" or ">&STDOUT" is given then the STDOUT filehandle is
used for output (and no open or close is performed). If
the special output filename ">&STDERR" is given then the
STDERR filehandle is used for output (and no open or close
is performed). If no output filehandle is currently in use
and no output filename is specified, then "-" is implied.

This method does not usually need to be overridden by sub
classes.

ACCESSOR METHODS

Clients of Pod::Parser should use the following methods to access instance data fields:

eerrrroorrssuubb(())

$parser->errorsub("method_name");
$parser->errorsub(warn_user);
$parser->errorsub(sub { print STDERR, @_ });

Specifies the method or subroutine to use when printing
error messages about POD syntax. The supplied method/sub
routine must return TRUE upon successful printing of the
message. If "undef" is given, then the warn builtin is
used to issue error messages (this is the default behav
ior).

my $errorsub = $parser->errorsub()
my $errmsg = "This is an error message!0
(ref $errorsub) and &{$errorsub}($errmsg)

or (defined $errorsub) and $parser->$er

rorsub($errmsg)

or warn($errmsg);

Returns a method name, or else a reference to the usersupplied subroutine used to print error messages. Returns
"undef" if the warn builtin is used to issue error mes
sages (this is the default behavior).

ccuuttttiinngg(())

$boolean = $parser->cutting();

Returns the current "cutting" state: a boolean-valued
scalar which evaluates to true if text from the input file
is currently being "cut" (meaning it is not considered
part of the POD document).

$parser->cutting($boolean);

Sets the current "cutting" state to the given value and
returns the result.

ppaarrsseeooppttss(())
When invoked with no additional arguments, parseopts returns a hashtable of all the current parsing options.

## See if we are parsing non-POD sections as

well as POD ones
my %opts = $parser->parseopts();
$opts{'-want_nonPODs}' and print "-want_non

PODs0;

When invoked using a single string, parseopts treats the string as the name of a parse-option and returns its cor
responding value if it exists (returns "undef" if it
doesn't).

## Did we ask to see '=cut' paragraphs?
my $want_cut = $parser->parseopts('-pro

cess_cut_cmd');
$want_cut and print "-process_cut_cmd0;

When invoked with multiple arguments, parseopts treats them as key/value pairs and the specified parse-option
names are set to the given values. Any unspecified parseoptions are unaffected.

## Set them back to the default
$parser->parseopts(-warnings => 0);

When passed a single hash-ref, parseopts uses that hash to completely reset the existing parse-options, all previous
parse-option values are lost.

## Reset all options to default
$parser->parseopts( { } );

See "PARSING OPTIONS" for more information on the name and
meaning of each parse-option currently recognized.

oouuttppuutt__ffiillee(())

$fname = $parser->output_file();

Returns the name of the output file being written.

oouuttppuutt__hhaannddllee(())

$fhandle = $parser->output_handle();

Returns the output filehandle object.

iinnppuutt__ffiillee(())

$fname = $parser->input_file();

Returns the name of the input file being read.

iinnppuutt__hhaannddllee(())

$fhandle = $parser->input_handle();

Returns the current input filehandle object.

PRIVATE METHODS AND DATA

Pod::Parser makes use of several internal methods and data fields which clients should not need to see or use. For
the sake of avoiding name collisions for client data and
methods, these methods and fields are briefly discussed
here. Determined hackers may obtain further information
about them by reading the Pod::Parser source code.

Private data fields are stored in the hash-object whose
reference is returned by the nneeww(()) constructor for this class. The names of all private methods and data-fields
used by Pod::Parser begin with a prefix of "_" and match the regular expression "/^_96

TREE-BASED PARSING

If straightforward stream-based parsing wont meet your
needs (as is likely the case for tasks such as translating
PODs into structured markup languages like HTML and XML)
then you may need to take the tree-based approach. Rather
than doing everything in one pass and calling the iinntteerrppoo_ llaattee(()) method to expand sequences into text, it may be desirable to instead create a parse-tree using the
ppaarrssee__tteexxtt(()) method to return a tree-like structure which may contain an ordered list of children (each of which may
be a text-string, or a similar tree-like structure).

Pay special attention to "METHODS FOR PARSING AND PROCESS
ING" and to the objects described in Pod::InputObjects.
The former describes the gory details and parameters for
how to customize and extend the parsing behavior of
Pod::Parser. Pod::InputObjects provides several objects that may all be used interchangeably as parse-trees. The
most obvious one is the Pod::ParseTree object. It defines the basic interface and functionality that all things try
ing to be a POD parse-tree should do. A Pod::ParseTree is defined such that each "node" may be a text-string, or a
reference to another parse-tree. Each Pod::Paragraph object and each Pod::InteriorSequence object also supports the basic parse-tree interface.

The ppaarrssee__tteexxtt(()) method takes a given paragraph of text, and returns a parse-tree that contains one or more chil
dren, each of which may be a text-string, or an Interi
orSequence object. There are also callback-options that
may be passed to ppaarrssee__tteexxtt(()) to customize the way it expands or transforms interior-sequences, as well as the
returned result. These callbacks can be used to create a
parse-tree with custom-made objects (which may or may not
support the parse-tree interface, depending on how you
choose to do it).

If you wish to turn an entire POD document into a
parse-tree, that process is fairly straightforward. The
ppaarrssee__tteexxtt(()) method is the key to doing this successfully. Every paragraph-callback (i.e. the polymorphic methods for
ccoommmmaanndd(()), vveerrbbaattiimm(()), and tteexxttbblloocckk(()) paragraphs) takes a Pod::Paragraph object as an argument. Each paragraph object has a ppaarrssee__ttrreeee(()) method that can be used to get or set a corresponding parse-tree. So for each of those
paragraph-callback methods, simply call ppaarrssee__tteexxtt(()) with the options you desire, and then use the returned parsetree to assign to the given paragraph object.

That gives you a parse-tree for each paragraph - so now
all you need is an ordered list of paragraphs. You can
maintain that yourself as a data element in the
object/hash. The most straightforward way would be simply
to use an array-ref, with the desired set of custom
"options" for each invocation of parse_text. Let's assume the desired option-set is given by the hash %options. Then
we might do something like the following:

package MyPodParserTree;

@ISA = qw( Pod::Parser );

...

sub begin_pod {

my $self = shift;
$self->{'-paragraphs'} = []; ## initialize para

graph list

}

sub command {

my ($parser, $command, $paragraph, $line_num,

$pod_para) = @_;
my $ptree = $parser->parse_text({%options}, $para

graph, ...);
$pod_para->parse_tree( $ptree );
push @{ $self->{'-paragraphs'} }, $pod_para;

}

sub verbatim {

my ($parser, $paragraph, $line_num, $pod_para) =

@_;
push @{ $self->{'-paragraphs'} }, $pod_para;

}

sub textblock {

my ($parser, $paragraph, $line_num, $pod_para) =

@_;
my $ptree = $parser->parse_text({%options}, $para

graph, ...);
$pod_para->parse_tree( $ptree );
push @{ $self->{'-paragraphs'} }, $pod_para;

}

...

package main;
...
my $parser = new MyPodParserTree(...);
$parser->parse_from_file(...);
my $paragraphs_ref = $parser->{'-paragraphs'};

Of course, in this module-author's humble opinion, I'd be
more inclined to use the existing Pod::ParseTree object than a simple array. That way everything in it, paragraphs
and sequences, all respond to the same core interface for
all parse-tree nodes. The result would look something
like:

package MyPodParserTree2;

...

sub begin_pod {

my $self = shift;
$self->{'-ptree'} = new Pod::ParseTree; ## ini

tialize parse-tree

}

sub parse_tree {

## convenience method to get/set the parse-tree

for the entire POD
(@_ > 1) and $_[0]->{'-ptree'} = $_[1];
return $_[0]->{'-ptree'};

}

sub command {

my ($parser, $command, $paragraph, $line_num,

$pod_para) = @_;
my $ptree = $parser->parse_text({<<options>>},

$paragraph, ...);
$pod_para->parse_tree( $ptree );
$parser->parse_tree()->append( $pod_para );

}

sub verbatim {

my ($parser, $paragraph, $line_num, $pod_para) =

@_;
$parser->parse_tree()->append( $pod_para );

}

sub textblock {

my ($parser, $paragraph, $line_num, $pod_para) =

@_;
my $ptree = $parser->parse_text({<<options>>},

$paragraph, ...);
$pod_para->parse_tree( $ptree );
$parser->parse_tree()->append( $pod_para );

}

...

package main;
...
my $parser = new MyPodParserTree2(...);
$parser->parse_from_file(...);
my $ptree = $parser->parse_tree;
...

Now you have the entire POD document as one great big
parse-tree. You can even use the -expand_seq option to parse_text to insert whole different kinds of objects. Just don't expect Pod::Parser to know what to do with them after that. That will need to be in your code. Or, alter
natively, you can insert any object you like so long as it
conforms to the Pod::ParseTree interface.

One could use this to create subclasses of Pod::Paragraphs and Pod::InteriorSequences for specific commands (or to create your own custom node-types in the parse-tree) and
add some kind of eemmiitt(()) method to each custom node/sub class object in the tree. Then all you'd need to do is
recursively walk the tree in the desired order, processing
the children (most likely from left to right) by format
ting them if they are text-strings, or by calling their
eemmiitt(()) method if they are objects/references.

SEE ALSO

Pod::InputObjects, Pod::Select

Pod::InputObjects defines POD input objects corresponding to command paragraphs, parse-trees, and inte
rior-sequences.

Pod::Select is a subclass of Pod::Parser which provides the ability to selectively include and/or exclude sections
of a POD document from being translated based upon the
current heading, subheading, subsubheading, etc.

AUTHOR

Brad Appleton <bradapp@enteract.com>

Based on code for Pod::Text written by Tom Christiansen <tchrist@mox.perl.com>

perl v5.8.0 2002-06-01 Pod::Parser(3)