I believe your problem with weak references has to do with the Spreadsheet::ParseExcel module wanting to compile some XS code -- which on Windows isn't possible unless you have an appropriate C compiler avilable. Failing that, presumably it falls back on a pure Perl solution, but it appears that fallback plan isn't working on Windows.

Hopefully someone more knowledgeable with this module will be able to comment -- I just wanted to post this to point you in what I believe is the right direction.