[PaulDavisThe1st]

Calling it an "internally developed macro language" is stretching it a little bit. It was an extremely simple blob of C++ code that scanned text looking for one of a very small number of known placeholders, and filled them in with the relevant value (session ID, user name, user email etc.) I suppose that over the years between 1996, the capabilities of catsubst may have been expanded somewhat, but certainly when it started there was no formal concept of it being a macro language. In fact, at the very beginning, we experimented with just using m4 (which is a formal macro language) but it wasn't quite right for the job.

[jrauser]

Fair enough. I maybe should have put language in scare quotes. :)