Before you start a rewrite, and if you are planning a rewrite, consider the decade we're in and what tools are available. While it's still used, CGI is an old technology. It has served the Internet well, was as ubiquitous as hydrogen in the early days, and is still maintained and nowadays but it's past its prime and there are more modern tools that allow you to develop with less effort.

Take on a small project with Mojolicious::Lite, and thank yourself for arriving at sanity later. For bigger projects, Mojolicious, Catalyst, Dancer, etc.

There will be a learning curve getting used to thinking in terms of Model/View/Controller, but once you get past the initial investment in learning you will be amazed at how much easier things have become.