A[] = key

Test(M) =
   A.foreach(key)
      M = $(M.add $(key), new)
      export M

   printvln($A)

   new = $(M.find key)
   if $(not $(equal $(new), new))
      println($"Error: A.foreach exports into A")
      exit 1

X. =
   extends $(Map)
   $|key| = old

Test($X)
