use MooseX::Declare;

class Point {    
    has x => ( isa => 'Int', is => 'rw' );
    has y => ( isa => 'Int', is => 'rw' );

    method negated   { $self->new( x => -$self->x, y => -$self->y ) }

    method transpose { $self->new( x => $self->y,  y => $self->x  ) }

    method inspect   { say $self->x . ' @ ' . $self->y              }
}

my $p = Point->new( x => 4, y => 3 );

$p->negated->inspect;      # => -4 @ -3
$p->transpose->inspect;    # => 3 @ 4

role Negated {
    requires 'transpose';
    method negated { $self->transpose };
}

Negated->meta->apply( $p );
$p->negated->inspect;      # => 3 @ 4
$p->transpose->inspect;    # => 3 @ 4