This useful article-> Automating-Web-based-Data-Retrieval-with-Perl ought to get you started. If you have difficulty, you can post your code here, and/or Google for perl Mechanize for more specific help.

UPDATE: It seems IBM's javascript page links are broken. :-( In the meantime Google for perl WWW::Mechanize tutorial

Update2: Here is a working link to the same Developer.com tutorial. -> Automating-Web-based-Data-Retrieval-with-Perl