I think you missed a reverse there:

push @_, @$last;
[download]

needs to be

push @_, reverse @$last;
[download]

since you are reversing the result. Trivial example: $last = [1,2,3,4,5] must flatten as 5, 4, 3, 2, 1 so it can be reversed in the final result to 1, 2, 3, 4, 5 again.

-- Randal L. Schwartz, Perl hacker