It isn't worth the hassle to implement the encryption in JavaScirpt. Suggest people use SSL, which is much more secure and reliable than anything you are going to come up with.

There is a big increase in complexity with doing the encryption in the browser. The form requires JavaScript, limiting who can use it. You will need to develop and test solution. You will likely run into variations in JavaScript implementations. You will need to get the JavaScript and Perl implementations to talk.

Doing the encryption in the browser doesn't buy you much security. Public-key encryption is probably too complicated to implement in the browser. Not to mention it requires multiple messages to do a proper key exchange. The simplest solution is to put the key in the page. But then the key is visible to packet sniffers.