content: on callback for arg
  	-- Returns a string like "arc has 3 letters"
  	arg & " has " & (count arg) & " letters"
  end callback
  
  set alist to {"arc", "be", "circle"}
  repeat with aref in alist
  	-- Passes a reference to some item in alist
  	-- to callback, then speaks the return value.
  	say (callback for aref)
  end repeat
  