NAME¶
Pod::Constants - Include constants from POD
SYNOPSIS¶
use vars qw($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 = 0.16;
=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
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()})
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.
FUNCTIONS¶
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} = $value;
}
},
import_from_file($filename, @args)¶
Very similar to straight "import", but you specify the source filename
explicitly.
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.
delete_hook(@list)¶
Deletes the named hooks. Companion function to add_hook
CLOSURES AS DESTINATIONS¶
If the given value is a ref CODE, then that function is called, with $_ set to
the value of the paragraph. This can be very useful for applying your own
custom mutations to the POD to change it from human readable text into
something your program can use.
After I added this function, I just kept on thinking of cool uses for it. The
nice, succinct code you can make with it is one of Pod::Constant's strongest
features.
Below are some examples.
EXAMPLES¶
Module Makefile.PL maintenance¶
Tired of keeping those module Makefile.PL's up to date? Note: This method seems
to break dh-make-perl.
Example Makefile.PL¶
eval "use Pod::Constants";
($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 => $AUTHOR) : ()),
);
Corresponding Module¶
=head1 NAME
MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness
=head2 MODULE RELEASE
This is release 1.05 of this module.
=head2 DEPENDENCIES
The following modules are required to make this module:
Some::Module => 0.02
=head2 AUTHOR
Ima Twat <ima@twat.name>
=cut
use vars qw($VERSION);
use Pod::Constants -trim => 1,
'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };
AUTHOR¶
Sam Vilain, <samv@cpan.org>
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
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