When the script is run with the --refresh-data option it will download the latest version of those files.
My personal preference on Debian/Ubuntu systems is to never install modules directly from CPAN. I use dh-make-perl to download the tarball, and build a .deb e.g.:
dh-make-perl --build --cpan Math::PlanePath
The .deb package can then be installed with dpkg or dropped into a repo. For a small hobby project like this it could be seen as overkill (although it's actually quick and easy). For bigger work-related projects it's invaluable to know that the same module version is being installed in dev, staging and production (rather than getting the latest version when you do your production rollout and getting a nasty surprise).