Sounds like you want your own development environment. I recommend compiling your own perl for that and giving it a prefix for installation. Personally I have everything in ~/installed/ with my path including ~/installed/bin. This lets me install perl cleanly and use it without disruption to the rest of the system (Debian makes heavy use of perl). Then when I run the cpan shell it pulls all its location stuff from Config.pm which conveniently points everything to ~/installed/. Inside of ~/installed, I keep a cpan directory and let CPAN use that as it's scratch space. All in all, it works well.