(commando/execute
  [commands-builtin/command-from-spec]
  {:items [{:__anchor "item" :price 10 :total {:commando/from ["@item" :price]}}
           {:__anchor "item" :price 20 :total {:commando/from ["@item" :price]}}]})
;; => {:items [{:__anchor "item", :price 10, :total 10}
;;             {:__anchor "item", :price 20, :total 20}]}

{:commando/from ["@section" "../" :base-price]}

(defmethod commando.commands.builtin/command-mutation :rand-n
  [_macro-type {:keys [v]}]
  (:instruction
   (commando.core/execute
     [commando.commands.builtin/command-apply-spec]
     {:commando/apply v
      := (fn [n] (rand-int n))})))

(defmethod commando.commands.builtin/command-macro :sum-n
  [_macro-type {:keys [v]}]
  {:__title "sum random"
   :commando/fn (fn [& v-coll] (apply + v-coll))
   :args [v
          {:commando/mutation :rand-n
           :v 200}]})

(print-trace
  #(commando.core/execute
     [commando.commands.builtin/command-fn-spec
      commando.commands.builtin/command-from-spec
      commando.commands.builtin/command-macro-spec
      commando.commands.builtin/command-mutation-spec]
     {:value {:commando/mutation :rand-n :v 200}
      :result {:commando/macro :sum-n
               :v {:commando/from [:value]}}}))