I am looking forward for item 24 "debugging Regex", and I hope it will cover perl's (use re 'debug') or python re.DEBUG flag. I still didn't find a satisfactory

I am looking forward for item 24 "debugging Regex", and I hope it will cover perl's (use re 'debug') or python re.DEBUG flag. I still didn't find a satisfactory document on the web on those features. I'd also like to see something on the eternal diatribe "regexp VS regular grammars", i.e. how the formers substantially differ from the latter. But maybe that's not the right book, having the (sane) "get it done" approach.