I found that trying to push as much stuff as possible into Perl is possible but usually not worth the effort, at least for SQL, Javascript and HTML.

Personally, I write those parts natively and include them, at least until I have completely understood the problem space. When using "integrated" solutions, I usually find myself running up to the limits of the integration and then fighting the framework that adapts Perl to whatever output I want, instead of actually solving the problem.

But if you're doing it for the fun of it, and for exploratory purposes, have a look at Jifty, which did lots of interesting high-traffic integration of Perl and Javascript, by generating Perl code to generate Javascript components from component templates.