You didn't edit your post to put the code in between <code>...</code> tags, which keeps it quite unreadable.

I saw just one line in the code that you should remove immediately and rewrite your code to work without it:

use Switch;
[download]

The Switch module is a bad idea that was propagated too far. It introduces subtle and hard to find bugs in any code that uses it. Just do not use it.

Also, you're not checking whether opening your files fails. It might help to output error messages in case opening a file (or opening a file through Excel) fails.