Yes, Win32::IE::Mechanize does do Javascript. It behaves a little oddly: code like document.write(...); includes both the original Javascript, as the generated result, in the "source". So it can't be a true compatible replacement for WWW::Mechanize... Once you take that behaviour into account, it works out very well.

An obvious limitation is that it only works on Windows, and you need an install of MSIE. But, given the former, the latter comes as a given. ;-)