@Glen_Kleidon2 gave a very cool presentation to Perth ADUG in the last week about regex - thanks very much Glen.
I hadn’t heard of regex comments before … and there seems to be an issue with using them in Delphi … so I was trying to find out some more about it. He pointed out that System.RegularExpressions was written by @vincent , and that System.RegularExpressionsCore was written by Jan Goyvaerts.
Searching online turned up “Regular Expressions - The Complete Tutorial - Jan Goyvaerts”.
Hi Paul
Thanks for the shout out - seems like a lifetime ago now (2009)! Most of the heavy lifting was done by Jan with his TPerlRegex library - I just wrote a nicer wrapper over it 
I edited the post to link to Jan’s site rather than share his pdf from a third party site - the pdf was shared on a user account at princeton - not sure that was entirely legal.
I wrote this blog post when XE was released - Getting Started with Delphi XE's Regular Expressions
I had planned to do a whole series of posts… but got too busy and forgot about it.
I also strongly recommend purchasing one of Jan Goyvaerts utilities for assisting you in writing regular expressions.
For those who want to write regular expressions quickly and fully understand how they work
www.regexbuddy.com
For those who want to write regular expressions quickly but aren’t as interested in understanding how they work
www.regexmagic.com
Both of these utilities let you write regular expressions of any flavour including of course Delphi.
Sorry about that. I didn’t know the name, so I had assumed he was actually an academic and that the link was legit.
My spider sense should probably have pricked up at the length - 200 pages. 
Maybe the title should be edited out also(?) … I can’t actually see the real book available online, or even at abebooks dot com
I see there are several books mentioned here … Books about Regular Expressions
Paul McGee
+1 for regexbuddy - has helped me many times.
I always use the site https://regex101.com/ for developing and testing regex. (Also to remember the various syntax.)
This site also has a library of expressions that you can implement or enhance, including RFC5322 email, telephone and password rules validation.