What kind of use cases have you had with the regexps that were not covered? (Just curious as I've not hit this). The builting regexp support can do many kinds o

What kind of use cases have you had with the regexps that were not covered? (Just curious as I've not hit this). The builting regexp support can do many kinds of advanced regexp things such as having a callback fn return the substitution or precompiling into regexp objects, lazily iterating over matches etc.