Old post but... I think this should work (for anyone who has a similar need). You can change the 1 to 0 if you want to avoid lines that begin with "0." as well. Also note that "aa." (or similar) will be matched/returned, since the request was to specifically avoid lines that start with a SINGLE letter (a, b, c, d) followed by a period. But this is easy to adjust as necessary if multiple letters followed by a period should also be skipped/avoided. ^(?![1-9]+\.|[a-d]\.).+$

why not this? ^[A-z]+\.[A-z]+\d{1,2}$