I for one would be very irretated if a module I install by hand (that is, not by CPAN, probably for a very good reason) tried to outsmart me and started using CPAN to pull in modules. Since you cannot know how someone's CPAN is configured or what the network policies are, this is a sure way of pissing off people.

Furthermore, you shouldn't assume perl is everywhere installed as 'root'. I seldomly install perl as root - I simply don't trust its complicated build and installation process (not to mention the dangers of CPAN) enough. I prefer having a decided account for it (which I typically call 'camel', member of the group 'perl'). I wouldn't be thrilled by a module whose Makefile says "oh, you're not root, let's install this module in some private module".

I'd say, just add a requisite in the Makefile. If people install the module with CPAN.pm, CPAN will pick up the requirement and either automatically install, or ask to install that module, depending on the installers preference. And if the installation goes by hand, the installer wouldn't mind a message saying which modules should be installed, giving the installer the option of how to install it.

Abigail