I'm looking at a kamailio config where all substdef have the syntax "!regexp!subst!flags", "!DB_URL!db.example.com!g" but i can't find this syntax in the documentation. It's currently running on a fairly modern 5.x version and as far as i know it has never been on 4.x or older.

Does anyone know where this syntax is from and if it's possible/recommended to simply replace it with "/regexp/subst"?