People have decided to conflate "functional" with "purity" in an odd way in this thread. Is OCaml now not functional?
I will leave discourse about the degree of purity that grants a "truly" moniker to people with more free time, but I suspect it's counter-productive.
What tipped you off? Was it setq, or perhaps nconc or delete?
For me, it was tagbody. I was like, "go ? Okay, this is still a functional language, but now way can I call it truly functional."