If the web page in question relies heavily on JavaScript, then you can't directly use Mechanize as it doesn't include a JavaScript engine - see WWW::Mechanize::FAQ. There are a couple of alternatives available. You might be able to use Win32::IE::Mechanize or Mozilla::Mechanize, which are supposed to offer external control over your browser. I've never used either, though it seems Win32::IE::Mechanize is better developed and tested. A more roll-you-own solution would use JavaScript::SpiderMonkey, but that's getting pretty hairy. Another choice is if figuring out how the page processes your userid and password and just crafting your own query string - I'd probably take this approach.

Determining success should be as simple as examining the content of the new page.