Nice synthesis of the advice you got!

In production code dealing with many searches on large strings you might want to make the .* match in the look ahead assertion non-greedy (.*?) so a search to the end of the string isn't required. Also, adding sort to (keys %words) gets the words in consistent order making it easier to find particular results if there are a lot of words.

Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

In reply to Re^2: regex, find words that occur more than once. by GrandFather
in thread regex, find words that occur more than once. by Anonymous Monk

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