local tHandlers = {
  ["B"] = turtle.back,
  ["D"] = turtle.down,
  ["F"] = turtle.forward,
  ["G"] = turtle.digUp,
  ["H"] = turtle.dig,
  ["I"] = turtle.digDown,
  ["L"] = turtle.turnLeft,
  ["O"] = turtle.placeUp,
  ["P"] = turtle.place,
  ["Q"] = turtle.placeDown,
  ["R"] = turtle.turnRight,
  ["U"] = turtle.up
}
 
function exec(command)
  if type(command) ~= "string" then return end
  for i = 1, #command do
    local cmd = tHandlers[command:sub(i,i)]
    if cmd then cmd() end
  end
end
