title: What is a flip-flop operator?
body: <p>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.</p>
  
  <p>Can anyone explain this in a language-agnostic manner?</p>
  
  <p>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?</p>