So I was giving this some thought on my commute this morning as I was stuck in traffic, and the list produced by your code actually has helped convince me even more. I think that there is a problem with ignoring the revision number.

As I looked over your list, I noticed at the bottom was a module of mine IOC. Now, rather then be flattered by this, I know that it's height on the list is quite artificial. I decided to adopt the XP idea of "release early and release often" with this module. The first released version (0.01) was on Oct. 15th of this year, and there have been 18 subsequent versions released, the last one on the 15th of Dec. and at least 10 versions have been released within the range of this log file (Nov. 1 - Dec. 15th). When I ran my script (see above) like this:

grep 'IOC' ~/Desktop/cpan-gets | perl test.pl
[download]

I got the following output:

+---------------------------------------
| Total Downloads by Module
+------+--------------------------------
|  609 | IOC
+---------------------------------------
| Total Downloads by Distro
+------+--------------------------------
|   10 | IOC-0.06.tar.gz
|   10 | IOC-0.01.tar.gz
|   10 | IOC-0.17.tar.gz
|   10 | IOC-0.03.tar.gz
|   10 | IOC-0.04.tar.gz
|   10 | IOC-0.05.tar.gz
|   11 | IOC-0.02.tar.gz
|   18 | IOC-0.07.tar.gz
|   44 | IOC-0.09.tar.gz
|   46 | IOC-0.13.tar.gz
|   50 | IOC-0.12.tar.gz
|   52 | IOC-0.14.tar.gz
|   54 | IOC-0.10.tar.gz
|   59 | IOC-0.08.tar.gz
|   64 | IOC-0.15.tar.gz
|   66 | IOC-0.11.tar.gz
|   85 | IOC-0.16.tar.gz
+------+--------------------------------
[download]

Clearly this module is not one of the top 100 on CPAN.

I think we need to give some thought as to how to include revisions into the analysis. My first thought is to maybe take the number of revisions found on the list, and to use that to somehow weight the results. The more revisions the less weight basically. Another thought is to somehow account for the number of downloads per-revision. As I mentioned above, the fact each revision is being downloaded shows that someone is following the development of the module, and so that should taken into account.

In the end I agree, this is going to be a mixture of art and science to come up with these top 100.