I have heard and read about flip-flops with regular expressions in Perl and Ruby recently, but I was unable to find how they really work and what the common use cases are.

Can anyone explain this in a language-agnostic manner?

Now that I understand what it is, and how it works, I would rephrase the question to be simply: What is a flip-flop operator?

ruby regex perl language-agnostic flip-flop
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