Well, that's just what many CGI::Application
Since I started using CGI::Application a little over two years ago I find that I can get massive code re-use. Using things like Class::DBI and the many CGI::Application plug-ins now available I find that I can produce a complete web application in as little as 50 or 60 lines of code. Plus the HTML templates of course. By combining HTML::Template (I know, everybody tells me to use Template::Toolkit, but I am comfortable with HTML::Template), the session management and authenticaion plug-ins, CSS and a collection of common support modules, I have been known to produce complete 10 form applications inside a day.
Maintenance time is drastically reduced as well. By factoring out all the common code into another set of modules, and having the runmodes as small as possible I find that a 20,000 line CGI::Application based product is vastly easier to maintain than its 20,000 line conventional CGI predecessor which I still maintain for one client.