If this is a legacy system without a substantial upgrade/conversion budget, my recommendation is to leave it as a separate isolated system running on the old, free Activestate perl while you plan, re-design and budget how to replace it.

Non Javascript in-line code has been out of style for many years - it is time to move on to modern frameworks which currently use REST/JSON interfaces, and Jquery/Bootstrap/Angular front-ends, possibly with perl/dancer2/mojo backends (or node.js and many other alternatives).