It's used here actually: 
my ($left,$middle,$right) = $sequence =~ m/(\w{$_})?(\w{1})?(\w*)/;
                                                ^

[download]
The result for 0..6 would be: 
              A  CTGACN
      A       C   TGACN
     AC       T    GACN
    ACT       G     ACN
   ACTG       A      CN
  ACTGA       C       N
 ACTGAC       N

[download]

In reply to Re^2: Equation - code review by imp
in thread Equation - code review by kulls

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