(defstruct AssetMissing [id i32])

(defvar cleanups i64)

(defn load [n i32] i32
  (signal (AssetMissing {:id n}))
  100)

(defn middle [n i32] i32
  (defer (set cleanups (+ cleanups 1)))   ; runs on the transfer too
  (+ (load n) 1))

(defn fetch [n i32] i32
  (restart-case (middle n)                ; its value if nothing transfers
    (use-placeholder [] -1)
    (retry           [] 7)))

(defn main []
  (print-i64 (i64 (fetch 1))) (newline)   ; 101 — nothing handled it

  (handler-bind [(AssetMissing [c] (invoke-restart 'use-placeholder))]
    (print-i64 (i64 (fetch 2))) (newline)) ; -1

  (print-i64 cleanups) (newline))         ; 2 — the defer ran both times