parameterization on methods...?

    subtype PStr,
      as Parameterizable[Str, Int),
      where { length(shift) < shift) };

    method(Int $length = 10)
        my_name(PStr[$length] $name)
    {
        return "Hello $name!";
    }

    say $self->my_name->with(5)->('JohnN');


    say $self->my_name(10,'JohnN'); ## "Hello JohnN!"
    say $self->my_name(2,'JohnN'); ## dies with constraint violation

    my $cb = $self->my_name(10);
    say $self->$cb('JohnN'); ## "Hello JohnN!"

    subtype UniqueID,
      as Parameterizable[Int, ResultSet],
      where { ! $_->[1]->find($_->[0]) };

    method(Object $rs = sub {shift->rs} )
        my_name(UniqueID[$rs] $id)
    {
        ## Something
    }