Thanks, but you missed the part of my OP where I say that I also need that solution in Python.

Frankly, I can't understand your insistence on this point: why does the fact that you must solve the problem both in Perl and in Python imply that you have to use a (pre-5.10) regex? Because it's the least common functionality, maybe? If so, then I see the point: code once, use twice.

The reason I looked for an regex was that the basic code already exists in Perl and Python and both scripts using split with a very simple regex to handle simple input which only supports points 1.-3. of the list in my OP, i.e. no quotes are handled etc., and as someone pointed out earlier '\,' is always taken as ',' even if the backslash itself got escaped like in '\\,'.

I was now trying to improve the allowed input and thought it would be the easiest way to just use a more advanced regex. This would have had the advantage that it wouldn't be very difficult to convince the manager in charge to allow the change, which is basically an API change: "Just have to replace regex A with regex B.". (Ok, I know, this doesn't guaranty that it won't introduce new bugs or break existing code)

Anyway I wrote a simple parser now, which was much easier than I originally thought, and will suggest that it will be used. The rest isn't up to me.

Thanks for the feedback.
Martin