> I've no idea what all(@ar1) < any(@ar2) would be, I guess it would check that max(ar1) < max(ar2)?

It seems that it just expands the lists using the operator. The output from junctions is quite nice:

    > my @a = <1 2 3 4>;
    > my @b = <2 3>;
    > say all(@a) < any(@b);
    all(any(True, True), any(False, True), any(False, False), any(False, False))
    > say so all(@a) < any(@b);
    False