I find regexes with (metachar...) tricks in them hard to read -- I'm not much of a regexer; it's one of the more important holes in my understanding of perl. Therefore, I'd use $4||''. However, that's already been mentioned in this thread -- the actual point is that I think the empty while would be clearer if you put in a #empty while; the work is in the condition comment. Writing that as 1 while foo; is more idiomatic. In either case, a simple empty pair of braces isn't clear that you don't just have an implied #WRITEME... which I think is what's bothering you.