I cleverly forgot to declare @unsorted and @sorted. This is why one should (a) test code before posting and (b) use strict; and use warnings;.

They do wonders to prevent things like:

@array = (1,2,3,4,5,6,7,8,9);
$sum+= $_ foreach @array;
$mean = $sum/scalar(@aray);
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(Yes, I know scalar(@aray) is 0.)