$ ocaml
# #use "topfind";;
# #require "lwt,lwt.unix";;
# open Lwt;;
# let (wai, wak) = wait ();;
val wai : '_a Lwt.t = <abstr>
val wak : '_a Lwt.u = <abstr>
# Lwt_main.run (join [wai; fail Exit]);;
<висим>