I ran the first listing's code and it failed to sort the array. Here's the fix:

15  
16      # Return the difference (0 = same)
17      return $a_v - $b_v;
18  }
19
[download]

was originally :

15  
16      # Return the difference (0 = same)
17      return $a - $b;
18  }
19
[download]

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