prn: func [s] [print s  line: []]
forever
  [line: to-block form parse/all trim/lines input { ^-}
   while [not empty? line: head line]
     [either parse line [set x number!]
        [prn x]
        [forall line
           [if parse copy/part line 3
                     [set x number! set y number! set o word!]
              [either find {+-*/} to-string o
                 [change/part line do reform [x o y] 3]
                 [prn {error}]
               break ]]
         if empty? line [prn {error}] ]]]