I have a feeling that it has something to do with the 'action'-url contained in the form. Could that be true? and how do I implement it in my submit_form? I have being searching for examples but haven't found any relevant yet.
Maybe. You can try $mech->post($url); I think. If you're willing to use an external browser that interprets javascript, I would take a look at WWW::Mechanize::Firefox or WWW::Selenium