Not to be a party-pooper, yet it seems what you're looking to do is already a part of any number of eBay-API-aware modules. A quick search on CPAN pulls up a few, and you might want to look to them for a more stable interface; eBay wont change APIs too often, but can and will change the web pages without a moment's notice.

If you're new to Perl (I notice you mentioned getting this script from elsewhere), it might be a bit daunting, so forgive me if it's so.