Thanks for the replies. I think I am making progress. For background I am actually working on a C++ project using a library that has a Perl-compliant Regex class.
I thought I'd verify my expression was indeed Perl correct.
The perl 5.10 install I have here does not include Data:Dump. We have Data::Dumper but I don't know if it's comparable. But anyway I can't fully run the solutions as written.
But I have updated my C++ code to reflect the feedback.
But it does not handle "RepeatingGroup = LEI, out, Flatten". I get no match at all. But I did not use 
(?=.*(?<Flatten>\bFlatten\b))?

[download]
I used 
(?:\\s*,\\s*(?P<Flatten>\\bFlatten\\b))?

[download]
I may not be understanding lookahead syntax but it seems like the ".*" would match anything
I want to make sure spaces and commas only preced the match.

In reply to Re: Regex with lookahead by ericwsf
in thread Regex with lookahead by ericwsf

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