The first time you run cpan from the command line, you are prompted for answers to various questions. How do you automate cpan and install modules non-interactively from the beginning?
Since it hasn't been mentioned yet, cpanminus is a zero-conf cpan installer. And you can download a self-contained executable if it isn't available for your version control.
The cpanm executable is easily installed (as documented in the executable itself) with:
curl -L http://cpanmin.us | perl - --self-upgrade
# or
wget -O - http://cpanmin.us | perl - --self-upgrade