package OO;
use strict;
use warnings;

#       A constructor
sub oo_create {
        my $class = shift;

        bless {}, $class;
}

#       Set Data reference for current class
sub oo_set {
        my $obj = shift;
        my $val = shift;

        my $class = @_ ? shift : caller;

        $obj->{ $class } = $val;
}

#       Get Data reference for current class
sub oo_get {
        my $obj = shift;

        my $class = @_ ? shift : caller;

        $obj->{ $class };
}

1;

##</code><code>##

package Foo;
use base 'OO';

sub new {
    my $class = shift;
    ( my $self = $class->oo_create )->oo_set( [] );
    # array based object!

    $self
}

sub bar {
    my $self = shift;
    my $data = $self->oo_get;

    $data->[0] = shift if @_;

    $data->[0]
}