That's the first time I see a regular expression implementation with intersection, apart from my own from many, many moons ago. A pleasant surprise. I also had added a negation operator, which adds another level of unintuitive behavior. E.g., you might think that !a would block aa from matching, but it doesn't.
hfst (open source rewrite of the Xerox finite state toolkit) includes negation:
$ echo 'a b
c b
c d*' | hfst-regexp2fst > ab.fst
$ echo 'c ?+' | hfst-regexp2fst >cdotplus.fst
$ hfst-intersect ab.fst cdotplus.fst | hfst-expand -c3
cb
cd
cdd
cddd
cdddd
$ hfst-expand -c3 ab.fst
ab
cb
c
cd
cdd
cddd
The anagram operator is a new one for me. Nice.