The "unless" is used to prevent calling the constructor as an instance method. The constructor can ONLY be called on the class name. Thus

CGI::Armature::Storage->new($obj, $hash);
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will work while

$obj->new($obj, $hash);
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will cause a fatal error due to $self not being initialized.

edit: Dec 10 2007

Sorry about that. I will append an edited version of my code after this reply.

How is it a fatal error? It's effectively a semi-static variable, but I don't see any error checking code.

I would have expected something like croak( 'Cannot call constructor on instance' ) if blessed( $class );, but all I see is mixing a lexical declaration with a postfix conditional, which usually isn't the right thing.

I feel embarrased to admit that I hadn't tested the code myself. After testing and debugging I decided to simplify the design and change the way the method calls are dispatched.

package Bridge::Simple;

use strict;

sub new {
    my $class = shift;
    my $object_ref = shift;
    my $method_map = shift;
    my $self = {};
    $self->{$_} = $method_map->{$_} for keys %$method_map;
    $self->{object} = $object_ref;
    return bless($self, $class);
}

sub AUTOLOAD {
    my $self = shift;
    use vars '$AUTOLOAD';
    $AUTOLOAD =~ s/.*:://;
    my $method = $self->{$AUTOLOAD};
    return $self->{object}->$method(@_);
}

1;
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use Bridge::Simple;
use XML::Simple;

my $serialize_map = {
    serialize=>'XMLin',
    deserialize=>'XMLout',
};

my $serializer = Bridge::Simple->new(
    XML::Simple->new(
        suppressempty=>q{}, 
        noattr=>1
    ),
    $serialize_map,
);
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This snippet of client code instantiates a Serializer object with a method_map that maps "serialize" with "XMLout" and "deserialize" with "XMLin" using the options given to override the default options of XML::Simple.

use Bridge::Simple;
use YAML;

my $serialize_map = {
    serialize=>'Dump',
    deserialize=>'Load',
};

my $serializer = Bridge::Simple->new(
    YAML->new(),
    $serialize_map,
);
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This snippet of client code does the same thing using YAML as the serialization interface.

Client code for either serializer object would be identical.

$data = $serializer->serialize($data_hash);

$data_hash = $serializer->deserialize($data);
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