This is a hash of hashes of hashes (HoHoH), which could have content like:

$VAR1 = {
          '543210' => {
                   '212' => {
                              'http://www.webaddress.com/' => 42
                            }
                 }
        };
[download]

where the 543210 is a $campaign_id value, the 100 is a $skin_id value, and the http://www.webaddress.com/ is a $refr_url value.

Please forgive the guessing here, but it looks like the data structure might be used to track the frequency of a referring URL, based upon a(n) (advertising?) campaign id and skin id.

This structure might be queried to answer something like, "How many referrals came from http://www.webaddress.com/ during the 543210 campaign that involved skin 212?"

Hope this helps!