As far as the client is concerned, JavaServer Pages is identical to PHP, Perl, or even static HTML files. The result is a page of HTML that can be rendered and displayed, and the source of the data isn’t the reason for WWW::Mechanize failing to do what you want
Doesn’t work is useless as a problem description, and the issue could be pretty much anything. However, if the HTML is associated with some JavaScript (which is executed on the client system after the page has been retrieved and not on the server) then it may be more or less handicapped because WWW::Mechanize doesn’t support JavaScript. For that you will need to use WWW::Mechanize::Firefox or similar, which works by using a real instance of Firefox to render the HTML and execute any JavaScript
solved How do I crawl a website written in JSP (Java Server Pages) using Perl Script?