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Pod::Parser(3pm)                      Perl Programmers Reference Guide                      Pod::Parser(3pm)



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(\*STDIN)  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:

       • command()

       • verbatim()

       • textblock()

       • interior_sequence()

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

       If you need to perform any preprocessing of input before it is parsed you may want to override one or
       more of preprocess_line() and/or preprocess_paragraph().

       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 end_pod() method to process. You could use
       Pod::Parser for several passes with an appropriate state variable to control the operation for each
       pass. If your input source can't be reset to start at the beginning, you can store it in some other
       structure as a string or an array and have that structure implement a getline() method (which is all
       that parse_from_filehandle() 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 collisions.

       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 interpret 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 possible to use the Pod::Parser::parse_text
       function to do more sophisticated tree-based parsing. See "TREE-BASED PARSING".

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 parseopts() 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
          paragraphs that are not part of the POD-format documentation are not made available to the caller
          (not even using preprocess_paragraph()). Setting this option to a non-empty, non-zero value will
          allow preprocess_paragraph() to see non-POD sections of the input as well as POD sections. The
          cutting() method can be used to determine if the corresponding paragraph is a POD paragraph, 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 command() 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 follows:

command()
                   $parser->command($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 textblock() method with the command paragraph).

verbatim()
                   $parser->verbatim($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.

textblock()
                   $parser->textblock($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 implementations of this method will probably want
       to invoke either interpolate() or parse_text(), 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).

interior_sequence()
                   $parser->interior_sequence($seq_cmd,$seq_arg,$pod_seq);

       This method should be overridden by subclasses to take the appropriate action when an interior
       sequence is encountered. 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 interpolate() 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::InteriorSequence"
       object which contains further information about the interior sequence.  Please see Pod::InputObjects
       for details if you need to access this additional information.

       Subclass implementations of this method may wish to invoke the nested() 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 interior_sequence() 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-processing. These methods do not have to be overridden, but it may be useful for subclasses
       to take advantage of them.

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

       This is the constructor for Pod::Parser and its subclasses. 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 constructor 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 constructor is not recommended, but if you insist on
       being able to do this, then the subclass will need to override the new() constructor method. If you
       do override the constructor, you must be sure to invoke the initialize() 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 new() constructor, as in:

           my $parser1 = MyParser->new( MYDATA => $value1, MOREDATA => $value2 );
           my $parser2 = new MyParser( -myflag => 1 );

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

initialize()
                   $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()".

begin_pod()
                   $parser->begin_pod();

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

begin_input()
                   $parser->begin_input();

       This method is invoked by parse_from_filehandle() immediately 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 begin_pod().

end_input()
                   $parser->end_input();

       This method is invoked by parse_from_filehandle() immediately 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 end_pod().

end_pod()
                   $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.

preprocess_line()
                 $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 performed for this line.

       Please note that the preprocess_line() method is invoked before the preprocess_paragraph() method.
       After all (possibly preprocessed) lines in a paragraph have been assembled together and it has been
       determined that the paragraph is part of the POD documentation from one of the selected sections,
       then preprocess_paragraph() is invoked.

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

preprocess_paragraph()
                   $textblock = $parser->preprocess_paragraph($text, $line_num);

       This method should be overridden by subclasses that wish to perform any kind of preprocessing for
       each block (paragraph) 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
       preprocess_paragraph() returns, the current cutting state (which is returned by "$self->cutting()")
       is examined. If it evaluates to true then input text (including the given $text) is cut (not
       processed) until the next POD directive is encountered.

       Please note that the preprocess_line() method is invoked before the preprocess_paragraph() method.
       After all (possibly preprocessed) lines in a paragraph have been assembled 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 preprocess_paragraph() 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 subclasses may want to invoke them to
       exploit their functionality.

parse_text()
                   $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 corresponding to the beginning of $text.

       parse_text() 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::InteriorSequence.  The result returned is
       a parse-tree of type Pod::ParseTree. Please see Pod::InputObjects for more information about
       Pod::InteriorSequence and Pod::ParseTree.

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

       -expand_seq => code-ref|method-name
          Normally, the parse-tree returned by parse_text() will contain an unexpanded
          "Pod::InteriorSequence" object for each interior-sequence encountered. Specifying -expand_seq
          tells parse_text() to "expand" every interior-sequence it sees by invoking the referenced function
          (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 interiorsequence
          sequence object.  [NOTE: If the interior_sequence() method is specified, then it is invoked
          according to the interface specified in "interior_sequence()"].

       -expand_text => code-ref|method-name
          Normally, the parse-tree returned by parse_text() will contain a text-string for each contiguous
          sequence of characters outside of an interior-sequence. Specifying -expand_text tells parse_text()
          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 top-level 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.

interpolate()
                   $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.

       interpolate() merely invokes a private method to recursively 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.

parse_from_filehandle()
                   $parser->parse_from_filehandle($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 documentation 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 getline() 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 filehandle 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 current invocation of this
       method.

       This method does not usually need to be overridden by subclasses.

parse_from_file()
                   $parser->parse_from_file($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 parse_from_filehandle() 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.
       Filehandle references, or objects that support the regular IO operations (like "<$fh>" or
       "$fh-<Egt"getline>) are also accepted; the handles must already be opened.

       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.  Alternatively, filehandle references or
       objects that support the regular IO operations (like "print", e.g. IO::String) are also accepted; the
       object must already be opened.

       This method does not usually need to be overridden by subclasses.

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

errorsub()
                   $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/subroutine must return TRUE upon successful printing of the message. If "undef" is given, then
       the carp builtin is used to issue error messages (this is the default behavior).

                   my $errorsub = $parser->errorsub()
                   my $errmsg = "This is an error message!\n"
                   (ref $errorsub) and &{$errorsub}($errmsg)
                       or (defined $errorsub) and $parser->$errorsub($errmsg)
                           or  carp($errmsg);

       Returns a method name, or else a reference to the user-supplied subroutine used to print error
       messages. Returns "undef" if the carp builtin is used to issue error messages (this is the default
       behavior).

cutting()
                   $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.

parseopts()
       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_nonPODs\n";

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

                   ## Did we ask to see '=cut' paragraphs?
                   my $want_cut = $parser->parseopts('-process_cut_cmd');
                   $want_cut and print "-process_cut_cmd\n";

       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 parse-options 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, parseoptions,
       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.

output_file()
                   $fname = $parser->output_file();

       Returns the name of the output file being written.

output_handle()
                   $fhandle = $parser->output_handle();

       Returns the output filehandle object.

input_file()
                   $fname = $parser->input_file();

       Returns the name of the input file being read.

input_handle()
                   $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 new()
       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 "/^_\w+$/".

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 interpolate() method to
       expand sequences into text, it may be desirable to instead create a parse-tree using the parse_text()
       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 PROCESSING" 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 trying 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 parse_text() method takes a given paragraph of text, and returns a parse-tree that contains one
       or more children, each of which may be a text-string, or an InteriorSequence object. There are also
       callback-options that may be passed to parse_text() 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 parsetree
       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 parse_text() method is the key to doing this successfully. Every paragraph-callback (i.e. the
       polymorphic methods for command(), verbatim(), and textblock() paragraphs) takes a Pod::Paragraph
       object as an argument. Each paragraph object has a parse_tree() method that can be used to get or set
       a corresponding parse-tree. So for each of those paragraph-callback methods, simply call parse_text()
       with the options you desire, and then use the returned parse-tree 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 paragraph list
           }

           sub command {
               my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
               my $ptree = $parser->parse_text({%options}, $paragraph, ...);
               $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}, $paragraph, ...);
               $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;  ## initialize 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, alternatively, 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 emit()
       method to each custom node/subclass 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 formatting
       them if they are text-strings, or by calling their emit() method if they are objects/references.

CAVEATS
       Please note that POD has the notion of "paragraphs": this is something starting after a blank (read:
       empty) line, with the single exception of the file start, which is also starting a paragraph. That
       means that especially a command (e.g. "=head1") must be preceded with a blank line; "__END__" is not
       a blank line.

SEE ALSO
       Pod::InputObjects, Pod::Select

       Pod::InputObjects defines POD input objects corresponding to command paragraphs, parse-trees, and
       interior-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
       Please report bugs using <http://rt.cpan.org>.

       Brad Appleton <bradapp@enteract.com>

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

LICENSE
       Pod-Parser is free software; you can redistribute it and/or modify it under the terms of the Artistic
       License distributed with Perl version 5.000 or (at your option) any later version. Please refer to
       the Artistic License that came with your Perl distribution for more details. If your version of Perl
       was not distributed under the terms of the Artistic License, than you may distribute PodParser under
       the same terms as Perl itself.



perl v5.12.5                                     2012-11-03                                 Pod::Parser(3pm)