perl -le'$;=3;$;=~s/./$&?30:3/eg for 3..pop;print length$;' 12

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Replace command-line argument 12 with any positive integer N to get the Nth Fibonacci number. Starts getting pretty slow for me after N=30, by the nature of the algorithm.

Can you see how it works?

<Reveal this spoiler or all in this thread>

blokhead

In reply to Fibonacci numbers using regexes (threes are wild) by blokhead

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