Hey @boehmflute,
These plus Freidl's are listed in the books section of the KM Wiki's RegEx reference page.
I have all of them, plus several tomes on Perl.
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"Sams Teach Yourself Regular Expressions in 10 Minutes" by Ben Forta (Book)
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"Regular Expressions Cookbook" by Goyvaerts & Levithan (Book)
I'm Interested in these two, but I haven't had my hands on them yet.
Note -- “Mastering Regular Expressions” by Jeffry Friedl has its merits but is very technical and not really for beginners.
Reading about regular expressions helps develop vocabulary, but it is only through repeatedly working with them that one develops proficiency.
-Chris