I saw several modules while looking for something yesterday, but a quick search on CPAN gave me CPAN::Dependency as something that sounded quite promising for what you were describing. (And, if I find the others I ran across, I'll update and add them below as well.)

Hope that helps.

Update: 2011-02-23

The following modules also look to be in line with what you stated you were looking for:

• CPAN::FindDependencies
• Devel::ModInfo
• Module::Dependency

Update: 2011-02-24

After looking in my browser history at work, I found one of the other modules I had remembered seeing:

• Module::ScanDeps