diff --git a/src/action_exec.ml b/src/action_exec.ml
index 07ce145ade6..da671ed3d41 100644
--- a/src/action_exec.ml
+++ b/src/action_exec.ml
@@ -182,9 +182,11 @@ and exec_list l ~ectx ~dir ~env ~stdout_to ~stderr_to =
   | [t] ->
     exec t ~ectx ~dir ~env ~stdout_to ~stderr_to
   | t :: rest ->
-    (let stdout_to = Process.Output.multi_use stdout_to in
-     let stderr_to = Process.Output.multi_use stderr_to in
-     exec t ~ectx ~dir ~env ~stdout_to ~stderr_to) >>= fun () ->
+    let* () =
+      let stdout_to = Process.Output.multi_use stdout_to in
+      let stderr_to = Process.Output.multi_use stderr_to in
+      exec t ~ectx ~dir ~env ~stdout_to ~stderr_to
+    in
     exec_list rest ~ectx ~dir ~env ~stdout_to ~stderr_to
 
 let exec ~targets ~context ~env t =
diff --git a/src/context.ml b/src/context.ml
index 72d64a8ce06..19b33169561 100644
--- a/src/context.ml
+++ b/src/context.ml
@@ -247,8 +247,8 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
     in
     let get_tool_using_findlib_config prog =
       let open Option.O in
-      findlib_config >>= fun conf ->
-      Findlib.Config.get conf prog >>= fun s ->
+      let* conf = findlib_config in
+      let* s = Findlib.Config.get conf prog in
       match Filename.analyze_program_name s with
       | In_path | Relative_to_current_dir -> which s
       | Absolute -> Some (Path.of_filename_relative_to_initial_cwd s)
@@ -559,8 +559,7 @@ let create_for_opam ~root ~env ~env_nodes ~targets ~profile
     | None -> Utils.program_not_found "opam" ~loc:None
     | Some fn -> fn
   in
-  opam_version opam env
-  >>= fun version ->
+  let* version = opam_version opam env in
   let args =
     List.concat
       [ [ "config"; "env" ]
@@ -571,8 +570,7 @@ let create_for_opam ~root ~env ~env_nodes ~targets ~profile
       ; if version < (2, 0, 0) then [] else ["--set-switch"]
       ]
   in
-  Process.run_capture ~env Strict opam args
-  >>= fun s ->
+  let* s = Process.run_capture ~env Strict opam args in
   let vars =
     Dune_lang.parse_string ~fname:"<opam output>" ~mode:Single s
     |> Dune_lang.Decoder.(parse (list (pair string string)) Univ_map.empty)
diff --git a/src/dune_file.ml b/src/dune_file.ml
index c3dcb361980..5723f3dafc2 100644
--- a/src/dune_file.ml
+++ b/src/dune_file.ml
@@ -52,7 +52,7 @@ let relative_file =
 
 let variants_field =
   field_o "variants" (
-    Syntax.since Stanza.syntax (1, 9) >>= fun () ->
+    let* () = Syntax.since Stanza.syntax (1, 9) in
     located (list Variant.decode >>| Variant.Set.of_list))
 
 (* Parse and resolve "package" fields *)
@@ -904,30 +904,30 @@ module Library = struct
        and+ no_keep_locs = field_b "no_keep_locs"
                             ~check:(Syntax.deprecated_in Stanza.syntax (1, 7))
        and+ sub_systems =
-         return () >>= fun () ->
+         let* () = return () in
          Sub_system_info.record_parser ()
        and+ project = Dune_project.get_exn ()
        and+ dune_version = Syntax.get_exn Stanza.syntax
        and+ virtual_modules =
          field_o "virtual_modules" (
-           Syntax.since Stanza.syntax (1, 7)
-           >>= fun () -> Ordered_set_lang.decode)
+           Syntax.since Stanza.syntax (1, 7) >>>
+           Ordered_set_lang.decode)
        and+ implements =
          field_o "implements" (
-           Syntax.since Stanza.syntax (1, 7)
-           >>= fun () -> located Lib_name.decode)
+           Syntax.since Stanza.syntax (1, 7) >>>
+           located Lib_name.decode)
        and+ variant =
          field_o "variant" (
-           Syntax.since Stanza.syntax (1, 9)
-           >>= fun () -> located Variant.decode)
+           Syntax.since Stanza.syntax (1, 9) >>>
+           located Variant.decode)
        and+ default_implementation =
          field_o "default_implementation" (
-           Syntax.since Stanza.syntax (1, 9)
-           >>= fun () -> located Lib_name.decode)
+           Syntax.since Stanza.syntax (1, 9) >>>
+           located Lib_name.decode)
        and+ private_modules =
          field_o "private_modules" (
-           Syntax.since Stanza.syntax (1, 2)
-           >>= fun () -> Ordered_set_lang.decode)
+           let* () = Syntax.since Stanza.syntax (1, 2) in
+           Ordered_set_lang.decode)
        and+ stdlib =
          field_o "stdlib" (Syntax.since Stdlib.syntax (0, 1) >>> Stdlib.decode)
        in
@@ -2121,11 +2121,11 @@ module Stanzas = struct
       (let+ x = Dune_env.Stanza.decode in
        [Dune_env.T x])
     ; "include_subdirs",
-      (Dune_project.get_exn () >>= fun p ->
+      (let* project = Dune_project.get_exn () in
        let+ () = Syntax.since Stanza.syntax (1, 1)
        and+ t =
          let enable_qualified =
-           Option.is_some (Dune_project.find_extension_args p Coq.key) in
+           Option.is_some (Dune_project.find_extension_args project Coq.key) in
          Include_subdirs.decode ~enable_qualified
        and+ loc = loc in
        [Include_subdirs (loc, t)])
diff --git a/src/dune_package.ml b/src/dune_package.ml
index 3318344f208..e9f445c7ec8 100644
--- a/src/dune_package.ml
+++ b/src/dune_package.ml
@@ -277,11 +277,13 @@ module Or_meta = struct
 
   let decode ~dir =
     let open Dune_lang.Decoder in
-    (* fields @@ *)
     fields
-      (field_b "use_meta" >>= function
-       | true -> return Use_meta
-       | false -> decode ~dir >>| fun p -> Dune_package p)
+      (let* use_meta = field_b "use_meta" in
+       if use_meta then
+         return Use_meta
+       else
+         let+ package = decode ~dir in
+         Dune_package package)
 
   let load p = Vfile.load p ~f:(fun _ -> decode ~dir:(Path.parent_exn p))
 end
diff --git a/src/fiber/fiber.ml b/src/fiber/fiber.ml
index 6f0c80d388f..ec44a091a5d 100644
--- a/src/fiber/fiber.ml
+++ b/src/fiber/fiber.ml
@@ -210,15 +210,17 @@ let map t ~f = t >>| f
 let bind t ~f = t >>= f
 
 let both a b =
-  a >>= fun x ->
-  b >>= fun y ->
+  let* x = a in
+  let* y = b in
   return (x, y)
 
 let all l =
   let rec loop l acc =
     match l with
     | [] -> return (List.rev acc)
-    | t :: l -> t >>= fun x -> loop l (x :: acc)
+    | t :: l ->
+      let* x = t in
+      loop l (x :: acc)
   in
   loop l []
 
@@ -228,7 +230,9 @@ let map_all l ~f =
   let rec loop l acc =
     match l with
     | [] -> return (List.rev acc)
-    | x :: l -> f x >>= fun x -> loop l (x :: acc)
+    | x :: l ->
+      let* x = f x in
+      loop l (x :: acc)
   in
   loop l []
 
@@ -236,7 +240,9 @@ let map_all_unit l ~f =
   let rec loop l =
     match l with
     | [] -> return ()
-    | x :: l -> f x >>= fun () -> loop l
+    | x :: l ->
+      let* () = f x in
+      loop l
   in
   loop l
 
@@ -361,8 +367,8 @@ let collect_errors f =
     ~on_error:(fun e l -> e :: l)
 
 let finalize f ~finally =
-  wait_errors f >>= fun res ->
-  finally () >>= fun () ->
+  let* res = wait_errors f in
+  let* () = finally () in
   match res with
   | Ok x -> return x
   | Error () -> never
@@ -441,7 +447,7 @@ module Once = struct
     | Running fut -> Future.wait fut
     | Not_started f ->
       t.state <- Starting;
-      fork f >>= fun fut ->
+      let* fut = fork f in
       t.state <- Running fut;
       Future.wait fut
     | Starting ->
@@ -478,7 +484,7 @@ module Mutex = struct
     k ()
 
   let with_lock t f =
-    lock t >>= fun () ->
+    let* () = lock t in
     finalize f ~finally:(fun () -> unlock t)
 
   let create () =
diff --git a/src/file_bindings.ml b/src/file_bindings.ml
index 153bcfba957..e5f74657ad1 100644
--- a/src/file_bindings.ml
+++ b/src/file_bindings.ml
@@ -55,9 +55,9 @@ module Unexpanded = struct
       { src; dst = None }
     | List (_, [_; Atom (_, A "as"); _]) ->
       enter
-        (decode >>= fun src ->
+        (let* src = decode in
          keyword "as" >>>
-         decode >>= fun dst ->
+         let* dst = decode in
          return { src; dst = Some dst })
     | sexp ->
       of_sexp_error (Dune_lang.Ast.loc sexp)
diff --git a/src/installed_dune_file.ml b/src/installed_dune_file.ml
index b42dfcf8cd9..0009f375b03 100644
--- a/src/installed_dune_file.ml
+++ b/src/installed_dune_file.ml
@@ -59,7 +59,7 @@ let of_sexp =
   in
   sum
     [ "dune",
-      (version >>= fun version ->
+      (let* version = version in
        set (Syntax.key Stanza.syntax) version
          (let+ parsing_context = get_all
           and+ sub_systems = list raw
diff --git a/src/merlin.ml b/src/merlin.ml
index 94a131cc19d..91ece4781ce 100644
--- a/src/merlin.ml
+++ b/src/merlin.ml
@@ -144,16 +144,18 @@ let pp_flags sctx ~expander ~dir_kind { preprocess; libname; _ } =
     begin match action with
     | Run (exe, args) ->
       let open Option.O in
-      List.destruct_last args >>= (fun (args, input_file) ->
+      let* (args, input_file) = List.destruct_last args in
+      let* args =
         if String_with_vars.is_var input_file ~name:"input-file" then
           Some args
         else
-          None)
-      >>= fun args ->
-      Expander.Option.expand_path expander exe >>= fun exe ->
-      List.map ~f:(Expander.Option.expand_str expander) args
-      |> Option.List.all
-      >>= fun args ->
+          None
+      in
+      let* exe = Expander.Option.expand_path expander exe in
+      let* args =
+        List.map ~f:(Expander.Option.expand_str expander) args
+        |> Option.List.all
+      in
       (Path.to_absolute_filename exe :: args)
       |> List.map ~f:quote_for_merlin
       |> String.concat ~sep:" "
diff --git a/src/ocaml-config/dune b/src/ocaml-config/dune
index 1e97fd5f070..904abcf5883 100644
--- a/src/ocaml-config/dune
+++ b/src/ocaml-config/dune
@@ -1,5 +1,6 @@
 (library
  (name        ocaml_config)
  (public_name dune._ocaml_config)
+ (preprocess future_syntax)
  (libraries   stdune)
  (synopsis    "[Internal] Interpret the output of 'ocamlc -config'"))
diff --git a/src/ocaml-config/ocaml_config.ml b/src/ocaml-config/ocaml_config.ml
index 73b148be6af..afa48844181 100644
--- a/src/ocaml-config/ocaml_config.ml
+++ b/src/ocaml-config/ocaml_config.ml
@@ -228,7 +228,7 @@ module Vars = struct
         | None ->
           Error (Printf.sprintf "Unrecognized line: %S" line)
     in
-    loop [] lines >>= fun vars ->
+    let* vars = loop [] lines in
     Result.map_error (String.Map.of_list vars) ~f:(fun (var, _, _) ->
       Printf.sprintf "Variable %S present twice." var)
 
diff --git a/src/ordered_set_lang.ml b/src/ordered_set_lang.ml
index d0b09694da5..fe1d65910bf 100644
--- a/src/ordered_set_lang.ml
+++ b/src/ordered_set_lang.ml
@@ -67,10 +67,10 @@ module Parse = struct
         let+ to_remove = junk >>> many [] kind in
         Diff (Union (List.rev acc), to_remove)
       | Some _ ->
-        one kind >>= fun x ->
+        let* x = one kind in
         many (x :: acc) kind
     in
-    Stanza.file_kind () >>= fun kind ->
+    let* kind = Stanza.file_kind () in
     match kind with
     | Dune -> many [] kind
     | Jbuild -> one kind
@@ -85,7 +85,7 @@ module Parse = struct
   let without_include ~elt =
     generic ~elt ~inc:(
       enter
-        (loc >>= fun loc ->
+        (let* loc = loc in
          Errors.fail loc "(:include ...) is not allowed here"))
 end
 
diff --git a/src/predicate_lang.ml b/src/predicate_lang.ml
index 5c08ee4c4e7..0f9a11b5481 100644
--- a/src/predicate_lang.ml
+++ b/src/predicate_lang.ml
@@ -20,7 +20,7 @@ module Ast = struct
 
   let decode elt =
     let open Stanza.Decoder in
-    let elt = elt >>| fun e -> Element e in
+    let elt = let+ e = elt in Element e in
     let rec one (kind : Dune_lang.Syntax.t) =
       peek_exn >>= function
       | Atom (loc, A "\\") -> Errors.fail loc "unexpected \\"
@@ -61,10 +61,10 @@ module Ast = struct
         junk >>> many union [] kind >>| fun to_remove ->
         diff (k (List.rev acc)) to_remove
       | Some _ ->
-        one kind >>= fun x ->
+        let* x = one kind in
         many k (x :: acc) kind
     in
-    Stanza.file_kind () >>= fun kind ->
+    let* kind = Stanza.file_kind () in
     match kind with
     | Dune -> many union [] kind
     | Jbuild -> one kind
diff --git a/src/preprocessing.ml b/src/preprocessing.ml
index b3602b78dfe..070bf4ae4d4 100644
--- a/src/preprocessing.ml
+++ b/src/preprocessing.ml
@@ -373,9 +373,8 @@ let build_ppx_driver sctx ~dep_kind ~target ~dir_kind ~pps ~pp_names =
       (* Extend the dependency stack as we don't have locations at
          this point *)
       Dep_path.prepend_exn e (Preprocess pp_names))
-      (pps
-       >>= Lib.closure ~linking:true
-       >>= fun pps ->
+      (let* pps = pps in
+       let* pps = Lib.closure ~linking:true pps in
        match jbuild_driver with
        | None ->
          let+ driver =
diff --git a/src/print_diff.ml b/src/print_diff.ml
index 98d586285ea..6cfce63554e 100644
--- a/src/print_diff.ml
+++ b/src/print_diff.ml
@@ -26,13 +26,14 @@ let print ?(skip_trailing_cr=Sys.win32) path1 path2 =
     | None -> fallback ()
     | Some prog ->
       Format.eprintf "%a@?" Errors.print loc;
-      Process.run ~dir ~env:Env.initial Strict prog
-        (List.concat
-           [ ["-u"]
-           ; if skip_trailing_cr then ["--strip-trailing-cr"] else []
-           ; [ file1; file2 ]
-           ])
-      >>= fun () ->
+      let* () =
+        Process.run ~dir ~env:Env.initial Strict prog
+          (List.concat
+             [ ["-u"]
+             ; if skip_trailing_cr then ["--strip-trailing-cr"] else []
+             ; [ file1; file2 ]
+             ])
+      in
       fallback ()
   in
   match !Clflags.diff_command with
@@ -42,8 +43,7 @@ let print ?(skip_trailing_cr=Sys.win32) path1 path2 =
     let cmd =
       sprintf "%s %s %s" cmd (quote_for_shell file1) (quote_for_shell file2)
     in
-    Process.run ~dir ~env:Env.initial Strict sh [arg; cmd]
-    >>= fun () ->
+    let* () = Process.run ~dir ~env:Env.initial Strict sh [arg; cmd] in
     die "command reported no differences: %s"
       (if Path.is_root dir then
          cmd
@@ -56,16 +56,17 @@ let print ?(skip_trailing_cr=Sys.win32) path1 path2 =
       match Bin.which ~path:(Env.path Env.initial) "patdiff" with
       | None -> normal_diff ()
       | Some prog ->
-        Process.run ~dir ~env:Env.initial Strict prog
-          [ "-keep-whitespace"
-          ; "-location-style"; "omake"
-          ; if Lazy.force Colors.stderr_supports_colors then
-              "-unrefined"
-            else
-              "-ascii"
-          ; file1
-          ; file2
-          ]
-        >>= fun () ->
+        let* () =
+          Process.run ~dir ~env:Env.initial Strict prog
+            [ "-keep-whitespace"
+            ; "-location-style"; "omake"
+            ; if Lazy.force Colors.stderr_supports_colors then
+                "-unrefined"
+              else
+                "-ascii"
+            ; file1
+            ; file2
+            ]
+        in
         (* Use "diff" if "patdiff" reported no differences *)
         normal_diff ()
diff --git a/src/stanza.ml b/src/stanza.ml
index 21523a1b604..aba99b997f0 100644
--- a/src/stanza.ml
+++ b/src/stanza.ml
@@ -54,27 +54,28 @@ module Decoder = struct
     switch_file_kind
       ~jbuild:(enter t)
       ~dune:(
-      try_
-        t
-        (function
-          | Parens_no_longer_necessary _ as exn -> raise exn
-          | exn ->
-            try_
-              (enter
-                 (loc >>= fun loc ->
-                  (if is_record then
-                     peek >>= function
-                     | Some (List _) ->
-                       raise (Parens_no_longer_necessary (loc, exn))
-                     | _ -> t
-                   else
-                     t)
-                  >>= fun _ ->
-                  raise (Parens_no_longer_necessary (loc, exn))))
-              (function
-                | Parens_no_longer_necessary _ as exn -> raise exn
-                | _ -> raise exn))
-    )
+        try_
+          t
+          (function
+            | Parens_no_longer_necessary _ as exn -> raise exn
+            | exn ->
+              try_
+                (enter
+                   (let* loc = loc in
+                    let* _ =
+                      if is_record then
+                        peek >>= function
+                        | Some (List _) ->
+                          raise (Parens_no_longer_necessary (loc, exn))
+                        | _ -> t
+                      else
+                        t
+                    in
+                    raise (Parens_no_longer_necessary (loc, exn))))
+                (function
+                  | Parens_no_longer_necessary _ as exn -> raise exn
+                  | _ -> raise exn))
+      )
 
   let record parse =
     parens_removed_in_dune_generic (fields parse) ~is_record:true
diff --git a/src/stdune/result.ml b/src/stdune/result.ml
index 6c56c24a298..cb9a3aef453 100644
--- a/src/stdune/result.ml
+++ b/src/stdune/result.ml
@@ -43,12 +43,21 @@ let to_option = function
 let errorf fmt =
   Printf.ksprintf (fun x -> Error x) fmt
 
+let both a b =
+  match a with
+  | Error e -> Error e
+  | Ok a ->
+    match b with
+    | Error e -> Error e
+    | Ok b -> Ok (a, b)
+
 module O = struct
   let ( >>= ) t f = bind t ~f
   let ( >>| ) t f = map  t ~f
 
   let (let*) = (>>=)
   let (let+) = (>>|)
+  let (and+) = both
 end
 
 open O
diff --git a/src/stdune/result.mli b/src/stdune/result.mli
index a0967122eb4..119603ba7c1 100644
--- a/src/stdune/result.mli
+++ b/src/stdune/result.mli
@@ -27,6 +27,7 @@ module O : sig
   val ( >>= ) : ('a, 'error) t -> ('a -> ('b, 'error) t) -> ('b, 'error) t
 
   val (let*) : ('a, 'error) t -> ('a -> ('b, 'error) t) -> ('b, 'error) t
+  val (and+) : ('a, 'error) t -> ('b, 'error) t -> ('a * 'b, 'error) t
   val (let+) : ('a, 'error) t -> ('a -> 'b) -> ('b, 'error) t
 end
 
diff --git a/src/sub_system.ml b/src/sub_system.ml
index f0e0d11bbef..7a750898138 100644
--- a/src/sub_system.ml
+++ b/src/sub_system.ml
@@ -125,14 +125,15 @@ module Register_end_point(M : End_point) = struct
   let gen info (c : Library_compilation_context.t) =
     let open Result.O in
     let backends =
-      Lib.Compile.direct_requires c.compile_info >>= fun deps ->
-      Lib.Compile.pps             c.compile_info >>= fun pps  ->
-      (match M.Info.backends info with
-       | None -> Ok None
-       | Some l ->
-         Result.List.map l ~f:(M.Backend.resolve (Scope.libs c.scope))
-         >>| Option.some)
-      >>= fun written_by_user ->
+      let* deps = Lib.Compile.direct_requires c.compile_info in
+      let* pps = Lib.Compile.pps c.compile_info in
+      let* written_by_user =
+        match M.Info.backends info with
+         | None -> Ok None
+         | Some l ->
+           Result.List.map l ~f:(M.Backend.resolve (Scope.libs c.scope))
+           >>| Option.some
+      in
       M.Backend.Selection_error.or_exn ~loc:(M.Info.loc info)
         (M.Backend.select_extensible_backends
            ?written_by_user
diff --git a/src/syntax.ml b/src/syntax.ml
index eaafa7cdd40..ec6d9a1a67a 100644
--- a/src/syntax.ml
+++ b/src/syntax.ml
@@ -172,17 +172,17 @@ let desc () =
 
 let deleted_in t ver =
   let open Version.Infix in
-  get_exn t >>= fun current_ver ->
+  let* current_ver = get_exn t in
   if current_ver < ver then
     return ()
   else begin
-    desc () >>= fun (loc, what) ->
+    let* (loc, what) = desc () in
     Error.deleted_in loc t ver ~what
   end
 
 let deprecated_in t ver =
   let open Version.Infix in
-  get_exn t >>= fun current_ver ->
+  let* current_ver = get_exn t in
   if current_ver < ver then
     return ()
   else begin
@@ -192,17 +192,17 @@ let deprecated_in t ver =
 
 let renamed_in t ver ~to_ =
   let open Version.Infix in
-  get_exn t >>= fun current_ver ->
+  let* current_ver = get_exn t in
   if current_ver < ver then
     return ()
   else begin
-    desc () >>= fun (loc, what) ->
+    let+ (loc, what) = desc () in
     Error.renamed_in loc t ver ~what ~to_
   end
 
 let since ?(fatal=true) t ver =
   let open Version.Infix in
-  get_exn t >>= fun current_ver ->
+  let* current_ver = get_exn t in
   if current_ver >= ver then
     return ()
   else
diff --git a/src/workspace.ml b/src/workspace.ml
index 5460c71dcc5..61286f8ea87 100644
--- a/src/workspace.ml
+++ b/src/workspace.ml
@@ -7,7 +7,7 @@ let syntax = Stanza.syntax
 
 let env_field =
   field_o "env"
-    (Syntax.since syntax (1, 1) >>= fun () ->
+    (Syntax.since syntax (1, 1) >>>
      Dune_env.Stanza.decode)
 
 module Context = struct
@@ -59,7 +59,7 @@ module Context = struct
       and+ targets = field "targets" (list Target.t) ~default:[Target.Native]
       and+ profile = field "profile" string ~default:profile
       and+ toolchain =
-        field_o "toolchain" (Syntax.since syntax (1, 5) >>= fun () -> string)
+        field_o "toolchain" (Syntax.since syntax (1, 5) >>> string)
       and+ loc = loc
       in
       { targets
@@ -165,13 +165,12 @@ include Versioned_file.Make(struct type t = unit end)
 let () = Lang.register syntax ()
 
 let t ?x ?profile:cmdline_profile () =
-  Versioned_file.no_more_lang >>= fun () ->
-  env_field >>= fun env ->
-  field "profile" string ~default:Config.default_build_profile
-  >>= fun profile ->
+  let* () = Versioned_file.no_more_lang in
+  let* env = env_field in
+  let* profile =
+    field "profile" string ~default:Config.default_build_profile in
   let profile = Option.value cmdline_profile ~default:profile in
-  multi_field "context" (Context.t ~profile ~x)
-  >>| fun contexts ->
+  let+ contexts = multi_field "context" (Context.t ~profile ~x) in
   let defined_names = ref String.Set.empty in
   let merlin_context =
     List.fold_left contexts ~init:None ~f:(fun acc ctx ->
diff --git a/src/wrapped.ml b/src/wrapped.ml
index fc439d9da40..926ac930472 100644
--- a/src/wrapped.ml
+++ b/src/wrapped.ml
@@ -10,8 +10,8 @@ let decode =
     [ "true", return (Simple true)
     ; "false", return (Simple false)
     ; "transition",
-      Syntax.since Stanza.syntax (1, 2) >>= fun () ->
-      string >>| fun x -> Yes_with_transition x
+      Syntax.since Stanza.syntax (1, 2) >>>
+      let+ x = string in Yes_with_transition x
     ]
 
 let encode =