You can code the exact same thing in the same number of lines in p6. That was not the real point though. I don't think anyone was golfing. The p6 solution above has something yours doesn't, take and gather. By default (at least last week ;) ) take and gather are lazy.

sub cross (*$f, *@a) {
    return unless $f;
    @a or return @{$f}.map:{[$_]} ;            # Handle one argument.
    my @r = cross(@a);                        # Recurse.
    @$f.map:{my $l = $_ ; @r.map:{[$l, @$_]} }; # Distribute.
}

cross().perl.say;
cross([],[1]).perl.say;
cross([1,2]).perl.say;
cross([1,2],[3]).perl.say;
cross([1],[2],[3]).perl.say;
cross([1],[2],[3,4]).perl.say;
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