The /x mode (extended regexp) lets you use any amount of whitespace or commenting. I use that mode whenever a regex gets complicated enough to merit an explanat

The /x mode (extended regexp) lets you use any amount of whitespace or commenting. I use that mode whenever a regex gets complicated enough to merit an explanation (which is quickly), and also indent groups and whatnot. Examples of where I used this in the past are here: Complex password validation: https://gist.github.com/pmarreck/4c5f1076498da1a86062 https://gist.github.com/pmarreck/4c5f1076498da1a86062 Email header parsing: https://gist.github.com/pmarreck/8476538 https://gist.github.com/pmarreck/8476538 An attempt at a JSON validator (yeah, I know): https://gist.github.com/pmarreck/2775709 https://gist.github.com/pmarreck/2775709 Remember that commenting is not just for others, but also for "future you"!