sub cross {
    my @list = @_.reverse or return;
    gather {
        my $count = [*] 1, @_.map:{ .elems };
        for 0 .. $count - 1 -> $idx is copy {
            take [
                @_.map:{ ($idx, my $elem) = divmod($idx, .elems); .[$elem] }
            ].reverse;
        }
    }
}