sub root {
    my $self = shift;
    my $root = $self;
    $root = $_ while defined( $_ = $root->parent );
    $root //= $self;
    return $root;
}

##</code><code>##

sub grandparent {
    my $self = shift;
    my $parent = $self->parent // return;
    return $parent->parent;
}
...
if( my $gp = $obj->grandparent ) {
   ## use it;
}
else{
   ## take a different path
}