package MyPackage;
use strict;
our $VERSION = 0;

use Tie::Hash;
use base qw(Tie::ExtraHash);

# OO Interface

sub new {
  my $class = ref($_[0]) || $_[0];
  my $self = bless {}, $class;
  tie %$self, $class;
}

sub to_string { join ' ', %{$_[0]}; }

# Tie interface

sub STORE { $_[0][0]{$_[1]} = ucfirst($_[2]); }

1;

##</code><code>##

#!/usr/bin/perl -w
use strict;
use MyPackage;

my $p = MyPackage->new();
$$p{Hello} = "world";
print $p->to_string, "\n";