You just have a small typo in your script, I assume because you copied the first for-loop to produce the second one.. You forgot to change the $eu<=(scalar(@idold)/2-1); to $io<=(scalar(@idold)/2-1);.

In fact, two typos. I assume that <h2>New$idold[$io]/$typeold[$old]</h2> should actually be <h2>New$idold[$io]/$typeold[$io]</h2>, since that is the counter for that for-loop.

Note: using 'use warnings;' at the top of your script would have pointed out that you were using the $old variable only once, and might have led you to the solution. Also, scoping your variables properly (ie my $eu and my $io) would have helped, as it would have died with an Undefined variable error when encountering the $eu the second time around..

C.