Regex检查字符串中的前两个字符是否为字母

I'm new to actionscript and i cant seem to get the regex syntax right in actionscript3. The task is straight forward, i want to make sure that the first two characters in a given string are alphabets and nothing else. Here's what I'm doing and obviously it doesn't work or i wouldn't be here! ;-).I'm new to actionscript and i cant seem to get