[nerdponx]

If that is indeed the case, then is it any better than an existing format like MessagePack?

[JonChesterfield]

I expect going digging would reveal that csexp is decades older than msgpack. As a format I agree it doesn't look great though.

May 1997 for csexp. https://web.archive.org/web/20230219084819/http://people.csa...

Msgpack less clear, maybe 2008. JSON is 2000ish.