Sometimes I’ll be on an old box and need to install a CPAN perl module for something. But when starting up CPAN, it tries to hit a bunch of mirrors that no longer exist. I just found out that you can easily clear the CPAN configuration and have it re-ask you all of the inital configuration questions.  Simply use the command ‘o conf init’ at the cpan> prompt.
I usually install Bundle::CPAN first so that you get a bunch of the important stuff, then install whatever else you need.