use CGI::Carp 'fatalsToBrowser'; # <-- recommended

No it isn't. (Get rid of fatalsToBrowser. It is helpful in development, but has no business in live, client-facing code.)

Use Template Toolkit or HTML::Template and separate the HTML out of your code. That will shorten the code by about 90% and make it much more maintainable also.

Other than that, I only skimmed over it, so my feeling that there's a whole lot to clean up may or may not be justified.

Makeshifts last the longest.