I used it 25 years ago (!) to build a tool for provisioning servers from a configuration file, i.e. generating files in /etc using macro substitution. I'm sure

I used it 25 years ago (!) to build a tool for provisioning servers from a configuration file, i.e. generating files in /etc using macro substitution. I'm sure the kids are doing this more elegantly today, but it sure saved us a lot of time!