I seem to recall some discussions here on deviations between the math/compsci concept of Regular Expressions, and the actual implementation in the Perl engine. It seems like you have already hit upon a source to describe the former; for the latter, I suggest:

  1. Tutorials here to learn (and also Super Search for more examples)
  2. This site to experiment with what you've learned.

Update: example of one such discussion.

Dum Spiro Spero

In reply to Re: Simplifying regexes by GotToBTru
in thread Simplifying regexes by ExReg

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