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