求完善一个正规表达式

数字后面最多一个字母：测试代码
<script language="javascript" type="text/javascript">
  var arr=["A9","A99","A9A","AA9","AA99","AA9A"];
  var reg=/^[A-Z]{1,2}(?:\d[A-Z]{0,1}|\d{2})$/;
  for(var i=0;i<arr.length;i++)
  {
    alert(reg.test(arr[i]));
  }
</script>