Can you post more about what you're doing? I can tell you that eBay moving to more JS generated DOMs, so generally speaking you can't rely on content from a direct request. HTML::Tiny
will give you the same info as curl
or some other utlitiy, so if in doubt check that output.
Also, for eBay, you can get away with https://www.ebay.com/itm/$itemnum and don't need all that other garbage.
(update) Another thing to note is if you request an item that doesn't exist (any more), eBay redirects you rather than sending you just a 404.