As stated before, this "divide and conquer" (also see http://en.wikipedia.org/wiki/Divide_and_conquer_algorithm) approach can be applied to many problems, but you can also use hashes for this by maintaining your order in the values as such:

#!/usr/bin/perl

@a = qw(one two three);
%h = map({$_ => $count++} @a);
print "$_ => $h{$_}\n" foreach (keys(%h));
foreach (sort( {$h{$a} <=> $h{$b}} keys(%h))) {
   print "$_\n";
}
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Janitored by tye: Add CODE tags