mjgardner, 
#Perl has supported pluggable replacements for its #RegularExpression engine since the release of v5.10 in 2007: https://perldoc.perl.org/perlreapi
An @ietf compliant I-#Regexp subset would be very helpful for @Perl #developers implementing specifications like the draft #JSONPath standard: https://datatracker.ietf.org/doc/draft-ietf-jsonpath-base/
(There is already a JSONPath #CPAN module: https://metacpan.org/pod/JSON::Path) https://cosocial.ca/@timbray/110714888717469041