Lua elseif 无法正常工作

当我尝试使用elseif，它不起作用。在下面的代码中，无论用户输入哪个数字，唯一运行的代码是 if 语句下的代码。

io.write("do you want to convert from celsius to farenheit (1), or the other way around (2)?")
pref = io.read()
if pref == 1 then
  io.write("Hi there! what's your temperature in celsius? ")
  local cel = io.read()
  far = (cel*1.8+32)
  io.write("That temperature in farenheit is: " .. far)
elseif pref == 2 then
  io.write("Hi there! what's your temperature in farenheit? ")
  local far = io.read()
  cel = ((far-32)/1.8)
  print("That temperature in celsius is: " .. cel)
end

问题不在于elseif。问题是因为io.read()返回一个字符串。要么将其转换为数字：

pref = tonumber(io.read())

或者，比较pref with "1", "2"反而。