You're getting your server stuff confused with your client stuff. Anything that happens dynamically on the page after it's loaded will be done by Javascript. The Perl script that creates the page will need to print that Javascript along with the HTML of the page. (Or it could be in a separate .js file that's included by the page.) So figure out what your Javascript needs to be by creating a static HTML test page with radio buttons that do what you want; then when that works, have your CGI print what you came up with.

I would highly recommend that you look into jQuery. It's a framework for doing dynamic page manipulation that sits on top of Javascript and eliminates a lot of the frustration of the language. This kind of thing is a one-liner in jQuery.