Not so much differnt modules as different versions depending on what distrobution it was installed in.

It's not uncommon -- especially when modules get rolled into the standared "perl" distrobution -- but normally the standalone distributions are still maintained and have the latest greatest features (ie: CPAN comes with perl, but you don't want to have to upgrade perl everytime you want the latest improvements to CPAN.)

Test::More is a little unusual in that it has been included in a wide variety distributions -- everything from Wx to Palm::Progect to perl-5.8.0.

Looking a little deeper right now, it looks like Test::More got rolled into the Test::Simple, and that's the new "definitive" distribution.