[pod-constants.git] / lib / Pod / Constants.pm

# Copyright (C) 2001, 2002, 2007 Sam Vilain.  All Rights Reserved.
# This module is free software. It may be used, redistributed and/or
# modified under the terms of the Perl Artistic License, version 2 or
# later, OR the terms of the GNU General Public License, v3 or later.

package Pod::Constants;

use 5.006002;
use strict;
use warnings;

use base qw(Pod::Parser Exporter);
use Carp;

our $VERSION = 0.17;

# An ugly hack to go from caller() to the relevant parser state
# variable
my %parsers;

sub end_input {
	#my ($parser, $command, $paragraph, $line_num) = (@_);
	my $parser = shift;

	return unless $parser->{active};

	print "Found end of $parser->{active}\n" if $parser->{DEBUG};
	my $whereto = $parser->{wanted_pod_tags}->{$parser->{active}};
	print "\$_ will be set to:\n---\n$parser->{paragraphs}\n---\n" if $parser->{DEBUG};

	$parser->{paragraphs} =~ s/^\s*|\s*$//gs if $parser->{trimmed_tags}->{$parser->{active}};

	if (ref $whereto eq 'CODE') {
		print "calling sub\n" if $parser->{DEBUG};
		local ($_) = $parser->{paragraphs};
		$whereto->();
		print "done\n" if $parser->{DEBUG};
	} elsif (ref $whereto eq 'SCALAR') {
		print "inserting into scalar\n" if $parser->{DEBUG};
		$$whereto = $parser->{paragraphs};
	} elsif (ref $whereto eq 'ARRAY') {
		print "inserting into array\n" if $parser->{DEBUG};
		@$whereto = split /\n/, $parser->{paragraphs};
	} elsif (ref $whereto eq 'HASH') {
		print "inserting into hash\n" if $parser->{DEBUG};
		# Oh, sorry, should I be in LISP101?
		%$whereto = (
			map { map { s/^\s*|\s*$//g; $_ } split /=>/ } grep m/^
					 ( (?:[^=]|=[^>])+ )   # scan up to "=>"
					 =>
					 ( (?:[^=]|=[^>])+ =? )# don't allow more "=>"'s
					 $/x, split /\n/, $parser->{paragraphs},);
	} else { die $whereto }
	$parser->{active} = undef;
}

# Pod::Parser overloaded command
sub command {
	my ($parser, $command, $paragraph, $line_num) = @_;

	$paragraph =~ s/(?:\r\n|\n\r)/\n/g;

	print "Got command =$command, value=$paragraph\n" if $parser->{DEBUG};

	$parser->end_input() if $parser->{active};

	my ($lookup);
	# first check for a catch-all for this command type
	if ( exists $parser->{wanted_pod_tags}->{"*$command"} ) {
		$parser->{paragraphs} = $paragraph;
		$parser->{active} = "*$command";
	} elsif ($command =~ m/^(head\d+|item|(for|begin))$/) {
		if ( $2 ) {
			# if it's a "for" or "begin" section, the title is the
			# first word only
			($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s*(\S*)\s*(.*)/s;
		} else {
			# otherwise, it's up to the end of the line
			($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s*(\S[^\n]*?)\s*\n(.*)$/s;
		}

		# Look for a match by name
		if (defined $lookup && exists $parser->{wanted_pod_tags}->{$lookup}) {
			print "Found $lookup\n" if ($parser->{DEBUG});
			$parser->{active} = $lookup;
		} elsif ($parser->{DEBUG}) {
			local $^W = 0;
			print "Ignoring =$command $paragraph (lookup = $lookup)\n"
		}

	} else {
		# nothing
		print "Ignoring =$command (not known)\n" if $parser->{DEBUG};
	}
}

# Pod::Parser overloaded verbatim
sub verbatim {
	my ($parser, $paragraph, $line_num) = @_;
	$paragraph =~ s/(?:\r\n|\n\r)/\n/g;

	my $status = $parser->{active} ? 'using' : 'ignoring';
	print "Got paragraph: $paragraph ($status)\n" if $parser->{DEBUG};

	$parser->{paragraphs} .= $paragraph if defined $parser->{active}
}

# Pod::Parser overloaded textblock
sub textblock { goto \&verbatim }

sub import {
	my $class = shift;

	# if no args, just return
	return unless (@_);

	# try to guess the source file of the caller
	my $source_file;
	if (caller ne 'main') {
		(my $module = caller.'.pm') =~ s|::|/|g;
		$source_file = $INC{$module};
	}
	$source_file ||= $0;

	croak "Cannot find source file (guessed $source_file) for package ".caller unless -f $source_file;

	# nasty tricks with the stack so we don't have to be silly with
	# caller()
	unshift @_, $source_file;
	goto \&import_from_file;
}

sub import_from_file {
	my $filename = shift;

	my $parser = __PACKAGE__->new();

	$parser->{wanted_pod_tags} = {};
	$parser->{trimmed_tags} = {};
	$parser->{trim_next} = 0;
	$parser->{DEBUG} = 0;
	$parser->{active} = undef;
	$parsers{caller()} = $parser;

	$parser->add_hook(@_);

	print "Pod::Parser: DEBUG: Opening $filename for reading\n" if $parser->{DEBUG};
	open my $fh, '<', $filename or croak "cannot open $filename for reading; $!";

	$parser->parse_from_filehandle($fh, \*STDOUT);

	close $fh;
}

sub add_hook {
	my $parser;
	if (eval { $_[0]->isa(__PACKAGE__) }) {
		$parser = shift;
	} else {
		$parser = $parsers{caller()} or croak 'add_hook called, but don\'t know what for - caller = '.caller;
	}
	while (my ($pod_tag, $var) = splice @_, 0, 2) {
		#print "$pod_tag: $var\n";
		if (lc($pod_tag) eq '-trim') {
			$parser->{trim_next} = $var;
		} elsif ( lc($pod_tag) eq '-debug' ) {
			$parser->{DEBUG} = $var;
		} elsif (lc($pod_tag) eq '-usage') {
			# an idea for later - automatic "usage"
			#%wanted_pod_tags{@tags}
		} else {
			if ((ref $var) =~ /^(?:SCALAR|CODE|ARRAY|HASH)$/) {
				print "Will look for $pod_tag.\n" if $parser->{DEBUG};
				$parser->{wanted_pod_tags}->{$pod_tag} = $var;
				$parser->{trimmed_tags}->{$pod_tag} = 1 if $parser->{trim_next};
			} else {
				croak "Sorry - need a reference to import POD sections into, not the scalar value $var"
			}
		}
	}
}

sub delete_hook {
	my $parser;
	if (eval { $_[0]->isa(__PACKAGE__) }) {
		$parser = shift;
	} else {
		$parser = $parsers{caller()} or croak 'delete_hook called, but don\'t know what for - caller = '.caller;
	}
	while ( my $label = shift ) {
		delete $parser->{wanted_pod_tags}->{$label};
		delete $parser->{trimmed_tags}->{$label};
	}
}

1;
__END__

=encoding utf-8

=head1 NAME

Pod::Constants - Include constants from POD

=head1 SYNOPSIS

 our ($myvar, $VERSION, @myarray, $html, %myhash);

 use Pod::Constants -trim => 1,
     'Pod Section Name' => \$myvar,
     'Version' => sub { eval },
     'Some list' => \@myarray,
     html => \$html,
     'Some hash' => \%myhash;

 =head2 Pod Section Name

 This string will be loaded into $myvar

 =head2 Version

 # This is an example of using a closure.  $_ is set to the
 # contents of the paragraph.  In this example, "eval" is
 # used to execute this code at run time.
 $VERSION = 0.17;

 =head2 Some list

 Each line from this section of the file
 will be placed into a separate array element.
 For example, this is $myarray[2].

 =head2 Some hash

 This text will not go into the hash, because
 it doesn't look like a definition list.
     key1 => Some value (this will go into the hash)
     var2 => Some Other value (so will this)
     wtf = This won't make it in.

 =head2 %myhash's value after the above:

    ( key1 => "Some value (this will go into the hash)",
      var2 => "Some Other value (so will this)"          )

 =begin html <p>This text will be in $html</p>

 =cut

=head1 DESCRIPTION

This module allows you to specify those constants that should be
documented in your POD, and pull them out a run time in a fairly
arbitrary fashion.

Pod::Constants uses Pod::Parser to do the parsing of the source file.
It has to open the source file it is called from, and does so directly
either by lookup in %INC or by assuming it is $0 if the caller is
"main" (or it can't find %INC{caller()})

=head2 ARBITARY DECISIONS

I have made this code only allow the "Pod Section Name" to match
`headN', `item', `for' and `begin' POD sections.  If you have a good
reason why you think it should match other POD sections, drop me a
line and if I'm convinced I'll put it in the standard version.

For `for' and `begin' sections, only the first word is counted as
being a part of the specifier, as opposed to `headN' and `item', where
the entire rest of the line counts.

=head1 FUNCTIONS

=head2 import(@args)

This function is called when we are "use"'d.  It determines the source
file by inspecting the value of caller() or $0.

The form of @args is HOOK => $where.

$where may be a scalar reference, in which case the contents of the
POD section called "HOOK" will be loaded into $where.

$where may be an array reference, in which case the contents of the
array will be the contents of the POD section called "HOOK", split
into lines.

$where may be a hash reference, in which case any lines with a "=>"
symbol present will have everything on the left have side of the =>
operator as keys and everything on the right as values.  You do not
need to quote either, nor have trailing commas at the end of the
lines.

$where may be a code reference (sub { }), in which case the sub is
called when the hook is encountered.  $_ is set to the value of the
POD paragraph.

You may also specify the behaviour of whitespace trimming; by default,
no trimming is done except on the HOOK names.  Setting "-trim => 1"
turns on a package "global" (until the next time import is called)
that will trim the $_ sent for processing by the hook processing
function (be it a given function, or the built-in array/hash
splitters) for leading and trailing whitespace.

The name of HOOK is matched against any "=head1", "=head2", "=item",
"=for", "=begin" value.  If you specify the special hooknames "*item",
"*head1", etc, then you will get a function that is run for every 

Note that the supplied functions for array and hash splitting are
exactly equivalent to fairly simple Perl blocks:

Array:

  HOOK => sub { @array = split /\n/, $_ }

Hash:

  HOOK => sub {
  %hash =
      (map { map { s/^\s+|\s+$//g; $_ } split /=>/, $_ }
        (grep m/^
            ( (?:[^=]|=[^>])+ )   # scan up to "=>"
            =>
            ( (?:[^=]|=[^>])+ =? )# don't allow more "=>"'s
            $/x, split /\n/, $_));
  }

Well, they're simple if you can grok map, a regular expression like
that and a functional programming style.  If you can't I'm sure it is
probably voodoo to you.

Here's the procedural equivalent:

  HOOK => sub {
     for my $line (split /\n/, $_) {
         my ($key, $value, $junk) = split /=>/, $line;
         next if $junk;
         $key =~ s/^\s+|\s+$//g
         $value =~ s/^\s+|\s+$//g
         $hash{$key} = $value;
     }
  },

=head2 import_from_file($filename, @args)

Very similar to straight "import", but you specify the source filename
explicitly.

=head2 add_hook(NAME => value)

This function adds another hook, it is useful for dynamic updating of
parsing through the document.

For an example, please see t/01-constants.t in the source
distribution.  More detailed examples will be added in a later
release.

=head2 delete_hook(@list)

Deletes the named hooks.  Companion function to add_hook

=head2 CLOSURES AS DESTINATIONS

If the given value is a ref CODE, then that function is called, with
$_ set to the value of the paragraph.  This can be very useful for
applying your own custom mutations to the POD to change it from human
readable text into something your program can use.

After I added this function, I just kept on thinking of cool uses for
it.  The nice, succinct code you can make with it is one of
Pod::Constant's strongest features.

Below are some examples.

=head1 EXAMPLES

=head2 Module Makefile.PL maintenance

Tired of keeping those module Makefile.PL's up to date?  Note: This
method seems to break dh-make-perl.

=head2 Example Makefile.PL

 eval "use Pod::Constants";
 ($Pod::Constants::VERSION >= 0.11)
     or die <<EOF
 ####
 ####  ERROR: This module requires Pod::Constants 0.11 or
 ####  higher to be installed.
 ####
 EOF

 my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
 Pod::Constants::import_from_file 
     (
      'MyTestModule.pm',
      'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
      'DEPENDENCIES' => ($PREREQ_PM = { }),
       -trim => 1,
      'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
      'AUTHOR' => \$AUTHOR,
     );

 WriteMakefile
     (
      'NAME'        => $NAME,
      'PREREQ_PM'        => $PREREQ_PM,
      'VERSION'          => $VERSION,
      ($] >= 5.005 ?    ## Add these new keywords supported since 5.005
       (ABSTRACT         => $ABSTRACT,
        AUTHOR           => $AUTHOR) : ()),
     );

=head2 Corresponding Module

 =head1 NAME

 MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness

 =head2 MODULE RELEASE

 This is release 1.05 of this module.

 =head2 DEPENDENCIES

 The following modules are required to make this module:

    Some::Module => 0.02

 =head2 AUTHOR

 Ima Twat <ima@twat.name>

 =cut

 our $VERSION;
 use Pod::Constants -trim => 1,
     'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };

=head1 AUTHOR

Sam Vilain, <samv@cpan.org>

=head1 BUGS/TODO

I keep thinking it would be nice to be able to import an =item list
into an array or something, eg for a program argument list.  But I'm
not too sure how it would be all that useful in practice; you'd end up
putting the function names for callbacks in the pod or something
(perhaps not all that bad).

Would this be useful?

 Pod::Constants::import(Foo::SECTION => \$myvar);

Debug output is not very readable

=head1 PATCHES WELCOME

If you have any suggestions for enhancements, they are much more likely
to happen if you submit them as a patch to the distribution.

Source is kept at

  git://utsl.gen.nz/Pod-Constants 


=cut
Commit	Line	Data
f46dd377 MG	1	# Copyright (C) 2001, 2002, 2007 Sam Vilain. All Rights Reserved.
	2	# This module is free software. It may be used, redistributed and/or
	3	# modified under the terms of the Perl Artistic License, version 2 or
	4	# later, OR the terms of the GNU General Public License, v3 or later.
	5
	6	package Pod::Constants;
	7
222de36b	8	use 5.006002;
f46dd377	9	use strict;
222de36b	10	use warnings;
f46dd377 MG	11
f46dd377 MG	12	use base qw(Pod::Parser Exporter);
f46dd377 MG	13	use Carp;
f46dd377 MG	14
222de36b	15	our $VERSION = 0.17;
f46dd377 MG	16
	17	# An ugly hack to go from caller() to the relevant parser state
	18	# variable
	19	my %parsers;
	20
	21	sub end_input {
db966dd0 MG	22	#my ($parser, $command, $paragraph, $line_num) = (@_);
	23	my $parser = shift;
	24
	25	return unless $parser->{active};
	26
612aada2	27	print "Found end of $parser->{active}\n" if $parser->{DEBUG};
db966dd0	28	my $whereto = $parser->{wanted_pod_tags}->{$parser->{active}};
612aada2	29	print "\$_ will be set to:\n---\n$parser->{paragraphs}\n---\n" if $parser->{DEBUG};
db966dd0	30
612aada2	31	$parser->{paragraphs} =~ s/^\s\|\s$//gs if $parser->{trimmed_tags}->{$parser->{active}};
db966dd0	32
fa6e78f4	33	if (ref $whereto eq 'CODE') {
db966dd0 MG	34	print "calling sub\n" if $parser->{DEBUG};
	35	local ($_) = $parser->{paragraphs};
	36	$whereto->();
	37	print "done\n" if $parser->{DEBUG};
fa6e78f4	38	} elsif (ref $whereto eq 'SCALAR') {
db966dd0 MG	39	print "inserting into scalar\n" if $parser->{DEBUG};
db966dd0 MG	40	$$whereto = $parser->{paragraphs};
fa6e78f4	41	} elsif (ref $whereto eq 'ARRAY') {
db966dd0 MG	42	print "inserting into array\n" if $parser->{DEBUG};
db966dd0 MG	43	@$whereto = split /\n/, $parser->{paragraphs};
fa6e78f4	44	} elsif (ref $whereto eq 'HASH') {
db966dd0 MG	45	print "inserting into hash\n" if $parser->{DEBUG};
db966dd0 MG	46	# Oh, sorry, should I be in LISP101?
612aada2	47	%$whereto = (
fa6e78f4	48	map { map { s/^\s\|\s$//g; $_ } split /=>/ } grep m/^
612aada2 MG	49	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
	50	=>
	51	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
fa6e78f4	52	$/x, split /\n/, $parser->{paragraphs},);
db966dd0 MG	53	} else { die $whereto }
db966dd0 MG	54	$parser->{active} = undef;
f46dd377 MG	55	}
	56
	57	# Pod::Parser overloaded command
	58	sub command {
db966dd0 MG	59	my ($parser, $command, $paragraph, $line_num) = @_;
	60
	61	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
	62
612aada2	63	print "Got command =$command, value=$paragraph\n" if $parser->{DEBUG};
db966dd0 MG	64
	65	$parser->end_input() if $parser->{active};
	66
db966dd0 MG	67	my ($lookup);
	68	# first check for a catch-all for this command type
	69	if ( exists $parser->{wanted_pod_tags}->{"*$command"} ) {
	70	$parser->{paragraphs} = $paragraph;
	71	$parser->{active} = "*$command";
db966dd0 MG	72	} elsif ($command =~ m/^(head\d+\|item\|(for\|begin))$/) {
	73	if ( $2 ) {
	74	# if it's a "for" or "begin" section, the title is the
	75	# first word only
612aada2	76	($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s(\S)\s(.)/s;
db966dd0 MG	77	} else {
db966dd0 MG	78	# otherwise, it's up to the end of the line
612aada2	79	($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s(\S[^\n]?)\s\n(.)$/s;
db966dd0 MG	80	}
	81
	82	# Look for a match by name
612aada2	83	if (defined $lookup && exists $parser->{wanted_pod_tags}->{$lookup}) {
db966dd0 MG	84	print "Found $lookup\n" if ($parser->{DEBUG});
db966dd0 MG	85	$parser->{active} = $lookup;
612aada2 MG	86	} elsif ($parser->{DEBUG}) {
	87	local $^W = 0;
	88	print "Ignoring =$command $paragraph (lookup = $lookup)\n"
db966dd0	89	}
f46dd377	90
f46dd377	91	} else {
db966dd0 MG	92	# nothing
db966dd0 MG	93	print "Ignoring =$command (not known)\n" if $parser->{DEBUG};
f46dd377	94	}
f46dd377 MG	95	}
	96
	97	# Pod::Parser overloaded verbatim
	98	sub verbatim {
db966dd0 MG	99	my ($parser, $paragraph, $line_num) = @_;
db966dd0 MG	100	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
f46dd377	101
fa6e78f4	102	my $status = $parser->{active} ? 'using' : 'ignoring';
612aada2	103	print "Got paragraph: $paragraph ($status)\n" if $parser->{DEBUG};
f46dd377	104
612aada2	105	$parser->{paragraphs} .= $paragraph if defined $parser->{active}
f46dd377 MG	106	}
	107
	108	# Pod::Parser overloaded textblock
	109	sub textblock { goto \&verbatim }
	110
f46dd377	111	sub import {
db966dd0 MG	112	my $class = shift;
	113
	114	# if no args, just return
	115	return unless (@_);
	116
	117	# try to guess the source file of the caller
	118	my $source_file;
fa6e78f4 MG	119	if (caller ne 'main') {
fa6e78f4 MG	120	(my $module = caller.'.pm') =~ s\|::\|/\|g;
db966dd0 MG	121	$source_file = $INC{$module};
	122	}
	123	$source_file \|\|= $0;
	124
612aada2	125	croak "Cannot find source file (guessed $source_file) for package ".caller unless -f $source_file;
db966dd0 MG	126
	127	# nasty tricks with the stack so we don't have to be silly with
	128	# caller()
	129	unshift @_, $source_file;
	130	goto \&import_from_file;
f46dd377 MG	131	}
f46dd377 MG	132
f46dd377	133	sub import_from_file {
db966dd0	134	my $filename = shift;
f46dd377	135
db966dd0	136	my $parser = __PACKAGE__->new();
f46dd377	137
db966dd0 MG	138	$parser->{wanted_pod_tags} = {};
	139	$parser->{trimmed_tags} = {};
	140	$parser->{trim_next} = 0;
	141	$parser->{DEBUG} = 0;
	142	$parser->{active} = undef;
	143	$parsers{caller()} = $parser;
f46dd377	144
db966dd0	145	$parser->add_hook(@_);
f46dd377	146
612aada2	147	print "Pod::Parser: DEBUG: Opening $filename for reading\n" if $parser->{DEBUG};
fa6e78f4	148	open my $fh, '<', $filename or croak "cannot open $filename for reading; $!";
f46dd377	149
db966dd0	150	$parser->parse_from_filehandle($fh, \*STDOUT);
f46dd377	151
db966dd0	152	close $fh;
f46dd377 MG	153	}
f46dd377 MG	154
f46dd377	155	sub add_hook {
db966dd0	156	my $parser;
fa6e78f4	157	if (eval { $_[0]->isa(__PACKAGE__) }) {
db966dd0	158	$parser = shift;
f46dd377	159	} else {
fa6e78f4	160	$parser = $parsers{caller()} or croak 'add_hook called, but don\'t know what for - caller = '.caller;
db966dd0 MG	161	}
	162	while (my ($pod_tag, $var) = splice @_, 0, 2) {
	163	#print "$pod_tag: $var\n";
fa6e78f4	164	if (lc($pod_tag) eq '-trim') {
db966dd0	165	$parser->{trim_next} = $var;
fa6e78f4	166	} elsif ( lc($pod_tag) eq '-debug' ) {
db966dd0	167	$parser->{DEBUG} = $var;
fa6e78f4	168	} elsif (lc($pod_tag) eq '-usage') {
db966dd0 MG	169	# an idea for later - automatic "usage"
	170	#%wanted_pod_tags{@tags}
	171	} else {
	172	if ((ref $var) =~ /^(?:SCALAR\|CODE\|ARRAY\|HASH)$/) {
612aada2	173	print "Will look for $pod_tag.\n" if $parser->{DEBUG};
db966dd0	174	$parser->{wanted_pod_tags}->{$pod_tag} = $var;
612aada2	175	$parser->{trimmed_tags}->{$pod_tag} = 1 if $parser->{trim_next};
db966dd0	176	} else {
fa6e78f4	177	croak "Sorry - need a reference to import POD sections into, not the scalar value $var"
db966dd0 MG	178	}
db966dd0 MG	179	}
f46dd377	180	}
f46dd377 MG	181	}
f46dd377 MG	182
f46dd377	183	sub delete_hook {
db966dd0	184	my $parser;
fa6e78f4	185	if (eval { $_[0]->isa(__PACKAGE__) }) {
db966dd0 MG	186	$parser = shift;
db966dd0 MG	187	} else {
fa6e78f4	188	$parser = $parsers{caller()} or croak 'delete_hook called, but don\'t know what for - caller = '.caller;
db966dd0 MG	189	}
	190	while ( my $label = shift ) {
	191	delete $parser->{wanted_pod_tags}->{$label};
	192	delete $parser->{trimmed_tags}->{$label};
	193	}
f46dd377 MG	194	}
f46dd377 MG	195
fa6e78f4	196	1;
49655cb6 MG	197	__END__
	198
	199	=encoding utf-8
	200
	201	=head1 NAME
	202
	203	Pod::Constants - Include constants from POD
	204
	205	=head1 SYNOPSIS
	206
612aada2	207	our ($myvar, $VERSION, @myarray, $html, %myhash);
49655cb6 MG	208
	209	use Pod::Constants -trim => 1,
	210	'Pod Section Name' => \$myvar,
	211	'Version' => sub { eval },
	212	'Some list' => \@myarray,
	213	html => \$html,
	214	'Some hash' => \%myhash;
	215
	216	=head2 Pod Section Name
	217
	218	This string will be loaded into $myvar
	219
	220	=head2 Version
	221
	222	# This is an example of using a closure. $_ is set to the
	223	# contents of the paragraph. In this example, "eval" is
	224	# used to execute this code at run time.
	225	$VERSION = 0.17;
	226
	227	=head2 Some list
	228
	229	Each line from this section of the file
	230	will be placed into a separate array element.
	231	For example, this is $myarray[2].
	232
	233	=head2 Some hash
	234
	235	This text will not go into the hash, because
	236	it doesn't look like a definition list.
	237	key1 => Some value (this will go into the hash)
	238	var2 => Some Other value (so will this)
	239	wtf = This won't make it in.
	240
	241	=head2 %myhash's value after the above:
	242
	243	( key1 => "Some value (this will go into the hash)",
	244	var2 => "Some Other value (so will this)" )
	245
	246	=begin html <p>This text will be in $html</p>
	247
	248	=cut
	249
	250	=head1 DESCRIPTION
	251
	252	This module allows you to specify those constants that should be
	253	documented in your POD, and pull them out a run time in a fairly
	254	arbitrary fashion.
	255
	256	Pod::Constants uses Pod::Parser to do the parsing of the source file.
	257	It has to open the source file it is called from, and does so directly
	258	either by lookup in %INC or by assuming it is $0 if the caller is
	259	"main" (or it can't find %INC{caller()})
	260
	261	=head2 ARBITARY DECISIONS
	262
	263	I have made this code only allow the "Pod Section Name" to match
	264	`headN', `item', `for' and `begin' POD sections. If you have a good
	265	reason why you think it should match other POD sections, drop me a
	266	line and if I'm convinced I'll put it in the standard version.
	267
	268	For `for' and `begin' sections, only the first word is counted as
	269	being a part of the specifier, as opposed to `headN' and `item', where
	270	the entire rest of the line counts.
	271
272	=head1 FUNCTIONS
273
274	=head2 import(@args)
275
276	This function is called when we are "use"'d. It determines the source
277	file by inspecting the value of caller() or $0.
278
279	The form of @args is HOOK => $where.
280
281	$where may be a scalar reference, in which case the contents of the
282	POD section called "HOOK" will be loaded into $where.
283
284	$where may be an array reference, in which case the contents of the
285	array will be the contents of the POD section called "HOOK", split
286	into lines.
287
288	$where may be a hash reference, in which case any lines with a "=>"
289	symbol present will have everything on the left have side of the =>
290	operator as keys and everything on the right as values. You do not
291	need to quote either, nor have trailing commas at the end of the
292	lines.
293
294	$where may be a code reference (sub { }), in which case the sub is
295	called when the hook is encountered. $_ is set to the value of the
296	POD paragraph.
297
298	You may also specify the behaviour of whitespace trimming; by default,
299	no trimming is done except on the HOOK names. Setting "-trim => 1"
300	turns on a package "global" (until the next time import is called)
301	that will trim the $_ sent for processing by the hook processing
302	function (be it a given function, or the built-in array/hash
303	splitters) for leading and trailing whitespace.
304
305	The name of HOOK is matched against any "=head1", "=head2", "=item",
306	"=for", "=begin" value. If you specify the special hooknames "*item",
307	"*head1", etc, then you will get a function that is run for every
308
309	Note that the supplied functions for array and hash splitting are
310	exactly equivalent to fairly simple Perl blocks:
311
312	Array:
313
314	HOOK => sub { @array = split /\n/, $_ }
315
316	Hash:
317
318	HOOK => sub {
319	%hash =
320	(map { map { s/^\s+\|\s+$//g; $_ } split /=>/, $_ }
321	(grep m/^
322	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
323	=>
324	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
325	$/x, split /\n/, $_));
326	}
327
328	Well, they're simple if you can grok map, a regular expression like
329	that and a functional programming style. If you can't I'm sure it is
330	probably voodoo to you.
331
332	Here's the procedural equivalent:
333
334	HOOK => sub {
335	for my $line (split /\n/, $_) {
336	my ($key, $value, $junk) = split /=>/, $line;
337	next if $junk;
338	$key =~ s/^\s+\|\s+$//g
339	$value =~ s/^\s+\|\s+$//g
340	$hash{$key} = $value;
341	}
342	},
343
344	=head2 import_from_file($filename, @args)
345
346	Very similar to straight "import", but you specify the source filename
347	explicitly.
348
349	=head2 add_hook(NAME => value)
350
351	This function adds another hook, it is useful for dynamic updating of
352	parsing through the document.
353
354	For an example, please see t/01-constants.t in the source
355	distribution. More detailed examples will be added in a later
356	release.
357
358	=head2 delete_hook(@list)
359
360	Deletes the named hooks. Companion function to add_hook
361
f46dd377 MG	362	=head2 CLOSURES AS DESTINATIONS
	363
	364	If the given value is a ref CODE, then that function is called, with
	365	$_ set to the value of the paragraph. This can be very useful for
	366	applying your own custom mutations to the POD to change it from human
	367	readable text into something your program can use.
	368
	369	After I added this function, I just kept on thinking of cool uses for
	370	it. The nice, succinct code you can make with it is one of
	371	Pod::Constant's strongest features.
	372
	373	Below are some examples.
	374
	375	=head1 EXAMPLES
	376
	377	=head2 Module Makefile.PL maintenance
	378
	379	Tired of keeping those module Makefile.PL's up to date? Note: This
	380	method seems to break dh-make-perl.
	381
	382	=head2 Example Makefile.PL
	383
	384	eval "use Pod::Constants";
	385	($Pod::Constants::VERSION >= 0.11)
	386	or die <<EOF
	387	####
	388	#### ERROR: This module requires Pod::Constants 0.11 or
	389	#### higher to be installed.
	390	####
	391	EOF
	392
	393	my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
	394	Pod::Constants::import_from_file
	395	(
	396	'MyTestModule.pm',
	397	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
e18addae	398	'DEPENDENCIES' => ($PREREQ_PM = { }),
f46dd377 MG	399	-trim => 1,
	400	'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
	401	'AUTHOR' => \$AUTHOR,
	402	);
	403
	404	WriteMakefile
	405	(
db966dd0	406	'NAME' => $NAME,
f46dd377 MG	407	'PREREQ_PM' => $PREREQ_PM,
	408	'VERSION' => $VERSION,
	409	($] >= 5.005 ? ## Add these new keywords supported since 5.005
	410	(ABSTRACT => $ABSTRACT,
	411	AUTHOR => $AUTHOR) : ()),
	412	);
	413
	414	=head2 Corresponding Module
	415
	416	=head1 NAME
	417
	418	MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness
	419
	420	=head2 MODULE RELEASE
	421
	422	This is release 1.05 of this module.
	423
e18addae	424	=head2 DEPENDENCIES
f46dd377 MG	425
	426	The following modules are required to make this module:
	427
	428	Some::Module => 0.02
	429
	430	=head2 AUTHOR
	431
	432	Ima Twat <ima@twat.name>
	433
	434	=cut
	435
222de36b	436	our $VERSION;
f46dd377 MG	437	use Pod::Constants -trim => 1,
	438	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };
	439
	440	=head1 AUTHOR
	441
	442	Sam Vilain, <samv@cpan.org>
	443
	444	=head1 BUGS/TODO
	445
	446	I keep thinking it would be nice to be able to import an =item list
	447	into an array or something, eg for a program argument list. But I'm
	448	not too sure how it would be all that useful in practice; you'd end up
	449	putting the function names for callbacks in the pod or something
	450	(perhaps not all that bad).
	451
	452	Would this be useful?
	453
	454	Pod::Constants::import(Foo::SECTION => \$myvar);
	455
	456	Debug output is not very readable
	457
	458	=head1 PATCHES WELCOME
	459
	460	If you have any suggestions for enhancements, they are much more likely
	461	to happen if you submit them as a patch to the distribution.
	462
	463	Source is kept at
	464
	465	git://utsl.gen.nz/Pod-Constants
	466
f46dd377	467
49655cb6	468	=cut