The problem is that something that works fine on one system breaks in another OS. It's pretty much like languages -- what's easy to write in Perl might not be so easy to write in Ruby, and visa-versa. The same with expressing ideas in French vs. English.
With systems, it's one thing to deal with a fresh install, and yet another to deal with a system that'd been used for years, with whatever's been installed, a few major OS updates, etc. In theory with MacOSX, it should just be a matter of installing the dev tools, and issuing the command 'sudo cpan'.
If you're manually installing the modules, it _will_not_ install dependancies, they might 'make' but they'll give errors when you 'make test'. (assuming the module author put in the appropriate tests).