The first half of your problem can be solved by not using sudo, but really become root (su -). Then root will use his own home directory.

An even better solution is not to install anything with cpan directly, but build a package that is native to your operating system. For Debian dh-make-perl is really useful, and very good usable in Testing (aka Lenny), I'm sure there are similar utilities for other distributions and Unixes (for example cpan2dist from CPANPLUS).