General remark: if you don't anchor your regexp ("^<regexp>" and/or "<regexp>$") there is no point in starting and ending with "[ \t]*", that would be ignored anyway. Either anchor it, and this makes sense, or make this character groups mandatory by using "+" instead of "*".

In this case, we don't want to match lines that are commented, so you want to use a start-of-line-anchored regexp.