devel/p5-Class-Multimethods-Pure 0.13_1 FreeBSD

You can define multimethods with the "multi" declarator:

use Class::Multimethods::Pure;

multi collide => ('Bullet', 'Ship') => sub {
    my ($a, $b) = @\_;  ...
};

multi collide => ('Ship', 'Asteroid') => sub {
    my ($a, $b) = @\_;  ...
};

It is usually wise to put such declarations within a BEGIN block, so they behave more like Perl treats subs (you can call them without parentheses and you can use them before you define them).