in reply to Histogramming the Perl Module Space
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:
Update: 2011-02-24
After looking in my browser history at work, I found one of the other modules I had remembered seeing:
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