sub display
{    my $self = shift;
    $self->displaynames($self->{root});
}

sub displaynames
{    my $self = shift;
    $head = shift;
    if (defined ($head->{LRef}))
    {    $self->displaynames($head->{LRef});
    }
    print $head->{Val}, "\n";
    if (defined ($head->{RRef}))
    {    $self->displaynames($head->{RRef});
    }
}