sub deep_copy
{
        my $self = shift;
        my $this = shift;
        unless (ref $this) {
                $this;
        } elsif (ref $this eq 'ARRAY') {
                [map $self->deep_copy($_), @$this];
        } elsif (ref $this eq 'HASH') {
                +{map{$_ => $self->deep_copy($this->{$_})} keys %$this};
        }
}

##</code><code>##

sub copy
{
        my $self = shift;
        return $self->deep_copy($self);
}