I think you missed the hint in the code: 

    ## $expr= "()"   if  @_ < 6;

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I noticed that there were only two numbers with unique solutions involving 6 terms. So we agreed that a number with only one solution would make the problem harder. I felt that more terms in that solution would also make it harder. But my statement of the puzzle was pretty vague.

[ And sure you can simplify the code if you hard-code three loops and hard-code the permutations. It runs fast enough that it'd be interesting to look at 4-digit terms next... ;) ]

                - tye

In reply to Re^2: Coming soon: Algorithm::Loops (puzzle2) by tye
in thread Coming soon: Algorithm::Loops by tye

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