Here's an easy one-liner which will automatically update all of the CPAN modules installed on your machine:

$ sudo perl -MCPAN -e 'CPAN::Shell->notest(install => CPAN::Shell->r)'

I always do it with sudo but you might not have to depending on your preferences.

Since waiting around for all of the tests to complete can be quite dull, I use notest() which might be considered risky by others.