Computer Craft turtle turn Program

local tArgs ={ ... }
if #tArgs == 0 then
    turtle.turnRight()
elseif #tArgs == 1 then
    if tArgs[1] == "right" or tArgs[1] == "90" then
        turtle.turnRight()
    elseif tArgs[1] == "left" or tArgs[1] == "-90" then
        turtle.turnLeft()
    elseif tArgs[1] == "180" then
        turtle.turnRight()
        turtle.turnRight()
    end
else
    print("Usage: 'turn' or 'turn [right/left/180/90/-90]")
end