TIMTOWTDI. 

print join ' ', '4744760012394122' =~ m[(....)]g
4744 7600 1239 4122

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Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller
If I understand your problem, I can solve it! Of course, the same can be said for you.

In reply to Re: Simple formatting question for credit card number by BrowserUk
in thread Simple formatting question for credit card number by Anonymous Monk

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