clearly the massive differences between tin2 and tin3 must at least alert you that something is wrong with the benchmark...

The problem is that his $b kept growing. You fixed it by readding my $b = 0;.

Which leads to two the second problem: He didn't use warnings. They don't add a penalty, so use them! If they did add a penalty, all the more reason to use them just like in the real code.

By the way,
$output[int($_/3)]
can be written as
$output[$_/3]