$regexp(a,.*?,+) = +++
while every flavor that I know (including Perl) outputs: +a+
From my understanding:
Since the dot is quantified by a lazy star (and there are no other tokens) it never matches any character (the token is skipped). The whole regex does match—however—twice. First it matches at character postion of 'a' and then at the very end of the string (regex engines tend to try to match a pattern even after all characters of the subject string have been used). Both matches are zero-width.
This does not happen in Mp3tag.
I don't know what's the logics here.
I know that this may sound a bit cryptic to ones not familiar with regular expressions. I'm not 100% sure of it myself. It may be a bug, it may be an oddity. Anyway an explanation on this would be much appreciated