invocable all

procedure main(stk,ws:' \t')
    while write("-> ",read() ? (while (pos(0) & break stk)        |
        push(stk, numeric(x := (tab(upto(~ws)),tab(many(~ws)))\1) |
                  proc(x,2)!push([],pop(stk),pop(stk)))           |
        break ["error"] )[1])
end