package Node;

sub new {
    my $class = shift;
    my $self = {};
    my $self->{parent} = undef;
    bless $self, $class;
    return $self;
}

sub parent {
    my $self = shift;
    if ( @_ ) {
        $self->{parent} = shift;
    }
    return $self;
}

##</code><code>##

use Node;

my ( $child, $parent ) = ( new Node, new Node );
$child->parent($parent);