Even for simple usage there might be CPAN modules that restrict the usage based on seemingly arbitrary qualification. AFAIK The Rules of CPAN do not say anything about what kind of licenses can be used for things uploaded.

If we write an app that us using CPAN modules we only have to take care of this. But actually we might distribute these modules by ourself (e.g. packaged by PAR or zipped together with a full Perl installation) to make it easier to deploy the application.

In such situation - I belive - one has to make sure he has the right to redistribute the original module in this packaged form.