The point of my example was to illustrate Perl and jQuery. To that end, I'm intentionally showing how much you can do in a small number of lines of code. I realize JSON and the Template Toolkit are very useful -- I frequently use both for adding features to Bugzilla at work -- but there wasn't any need for them in an example specifically limited to Perl and jQuery.

On top of that, by "dumbing down" the functionality, your example does nothing more than calculate whether a number is even or odd. You can do that on the client in javascript; why would you need jQuery, Ajax, JSON, the Template Toolkit and a call to the server for that?!