I'm not really sure where your question is about Perl.

Some general hints:

1. Benchmark to find where the bottleneck is. You're sending 7MB over the wire, which is a lot of data. Maybe split up the Javascript into smaller files that don't need to be loaded every access.
2. If you're generating the Javascript from Perl, look whether you can create the Javascript as static files, thus reducing the time it takes until the answer can be sent.
3. Consider eliminating the Javascript alltogether and only deliver information when it is requested instead of all information at once. This is the part where Perl is of most help I guess.

Now I remember why I use noscript. Isn't 7 meg getting a bit excessive for code that is just supposed to do minimal browser-side checking?

You really should follow the advice already given but I thought that I would share a few thoughts that came to mind when I read your post.

Split your JavaScript out into libraries so that you can only load the scripts that you need instead of sending everything every time. The browser will cache the libraries if you let it.

Use AJAX for page updates where it makes sense, like updating a selection box when a selection is made in another selection box.

If you are working with data and not HTML or JS snippets, then store and transmit it as JSON (JavaScript Object Notation -- you send a data structure that can be converted into a JS object). Once you have your JS object, it can be used or transformed however you like.