CMI: CGI or JSP?

System

I may have to write a custom menu item. Currently the server is 5.5.2 and there are many custom Perl modules, so Perl is the easy route. I could also go JSP (with a hidden HTML form written from Perl to repost the form data to the JSP). The only parameter I need is path_0, the selected file (I would also like path_1 to ensure they have not selected more than one file).

My question is, if I write this in CGI/Perl today, how much effort would be required to port it to 6.1 tomorrow? Should I just write it in JSP today even if that means a significantly increased development effort?

How can I write my CMI so that it works in 5.5.2 *and* 6.x? Are there instructions for this somewhere, or a list of issues for rewriting CGI CMIs for 6.x?