Tried out the 20 beta. I use @REGEXSUB heavily in my batch files and it is not functioning properly. Simplified example: In 17.00.77 x64, this returns "2". In 20beta it returns an empty string. I suppose this could have broken in 18 or 19, but given the change of regular expression library in 20 I think it's more likely that it's a regression in the beta.