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.