Here's what the current hash looks like (fragment). The 's' value points to a hash of locations.

$VAR1 = {
          '0 0 20 0 13 0 0 0 5' => {
                                     's' => {
                                              '0,7' => 1
                                            }
                                   },
          '0 0 18 1 0' => {
                            's' => {
                                     '0,6' => 1
                                   }
                          },
          '2 0 8 0 0 0 2' => {
                               's' => {
                                        '0,4' => 1
                                      }
                             },
          '0 42314 18 1 0' => {
                                's' => {
                                         '0,6' => 1
                                       }
                              },

...
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