As has previously been advised, read the WWW::Mechanize documentation:

http://search.cpan.org/dist/WWW-Mechanize/lib/WWW/Mechanize/FAQ.pod

Frequently asked questions. Make sure you read here FIRST.

The FAQ has a section: Why doesn't this work: Debugging your Mechanize program. I suggest you start there. If your debugging doesn't get you any further read How do I post a question effectively? and post again.