Xerox had xfst, which replaced regular expressions by regular _relations_, and offered named sub-expressions, which solved the regex "write only" problem. Xero

Xerox had xfst, which replaced regular expressions by regular _relations_, and offered named sub-expressions, which solved the regex "write only" problem. Xerox' original XRCE (Research Centre Europe) pages are gone, but other sites offer a glimpse, and FOMA is an open source implementation of the same language: [1] https://sites.google.com/a/utcompling.com/icl-f11/home/xfst-tutorial https://sites.google.com/a/utcompling.com/icl-f11/home/xfst-... [2] https://dsacl3-2018.github.io/xfst-demo/ https://dsacl3-2018.github.io/xfst-demo/