[%defer later]; now syntax.This is an OCaml language extension implementing a somewhat Go-ish [%defer expr1]; expr2 which will defer the evaluation of expr1 until after expr2. expr1 will still be evaluated if expr2 raises an exception.
If you are using Lwt you can use [%defer.lwt expr1]; expr2.
Thanks to Drup for guidance in figuring out ppx details!