speaking turtle greeting with rfid cards

rfid = peripheral.wrap("top")
speak = peripheral.wrap("left")
distance = 3
antiterm = false

known = {svenn = "SIA"}

function check(poo)
  for k,v in pairs(known) do
    if v == poo then
      return k
    end
  end
  return nil
end

if antiterm then
  os.pullEvent = os.pullEventRaw
end

while true do
  repeat
    rfid.scan(distance)
    event,param = os.pullEvent()
    if event == "rfid_detected" then
      ok = check(param)
      if ok ~= nil then
        speak.say("hello "..ok)
        os.startTimer(2)
        sleep(1.5)
      else
        speak.say("hello stranger")
        os.startTimer(2)
        sleep(1.5)
      end
    end
  until event == "rfid_scan_done" or event == "timer"
end