now this is podracing

save.eff

(* yeah, so, Eff doesn't actually support polymorphic effects *)

effect Save: string -> int
effect Load: string * int -> empty

let save name = perform (Save name)
let load name v = absurd (perform (Load (name, v)))

let savegames = handler
  | effect (Save name) k ->
      let rec loading () = handler
        | effect (Load (name', v)) _ ->
            if name = name'
              then
                with loading () handle
                continue k v
              else load name' v
      in
      with loading () handle
      continue k 0;;

with savegames handle
  match save "first_save" with
    | 0 ->
        print_endline "first this...";
        load "first_save" 23;
        print_endline "shouldn't make it here"
    | 23 ->
        begin match save "second_save" with
          | 0 ->
              print_endline "now this";
              load "second_save" 99;
              print_endline "shouldn't make it here"
          | n ->
              print_endline "followed by this";
              load "first_save" (n + 3);
              print_endline "nor here"
        end
    | n ->
        print_endline ("reloaded with: " ^ string_of_int n)
;;