{
    use class Point => ISA-LIST;

    my ($x, $y);
    my $z :ro;
    our @points; # class var 
    
    sub inverted :public {
        return Point->new( x => $$y, y => $$x );
    }

} #end of scope

##</code><code>##

my $old_meth = \&Point::inverted;

*Point::inverted = sub {
    $self = shift @_;
    $x = \ $self->{x};
    $y = \ $self->{y};
    goto &$old_meth;
}