I would venture to say that in most situations, the JavaScript/Perl route is the best/easiest way to go. However, you shouldn't rely entirely on JavaScript to do your validation. Client-side validation can be useful in the sense that it is user friendly, but you must protect yourself on the server-side since it is possible to bypass your JavaScript checks and invoke your CGI using bogus (potentially harmful) data.

There are all sorts of active scripting languages that could be used provided you meet all the necessary requirements (right platform, right web server software installed, etc.). E.G., PerlScript, VBScript and even CobolScript (as jcwren laments here).

This node, CGI and JavaScript, should also prove interesting reading.

HTH,

--Jim

Update: I see after I posted that you were planning to validate via Perl in any case. So pardon the rant on that count. :)