In Perl 6, => is a constructor for the built-in PAIR datatype (see: Apocalypse 3 and Exegesis 3).

Both arguments of the pair constructor are evaluated in scalar contexts. In the problem code above, that would cause the param method to be called in scalar context, which would cause its "empty return" to return undef instead of that pesky empty list.

So I guess the short answer is that it...

would just no longer be an issue there.