sub IncrData {
   my $key = shift;

   if (exists $data_refs_hash{$key} ) { # if there's a hash entry
      ${$data_refs_hash{$key}}++;       # increment it
   }
   else {   # otherwise, find a spot and put one in
      my $idx = 0;
      my $endIdx = scalar(@{$data[0]});
      while ($idx < $endIdx && $data[0][$idx] < $key) {
         $idx++;
      }
      splice(@{$data[0]},$idx,0,$key);
      splice(@{$data[1]},$idx,0,1);
      $data_refs_hash{$key} = \$data[1][$idx];
   }
   # if you need to update the sort each time, then do
   @{$data[2]} = sort { $a <=> $b } @{$data[1]};
   # but you shouldn't update it until you're going to use it, 
   # since it's expensive to sort for every increment

} # IncrData