The regex is:

(?:(?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))
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which contains no capturing groups, hence $1 isn't populated. In my first bit of code, in the regex I added an extra set of parentheses, /($RE{delimited}{-delim=>'"'})/, so there is a capturing group there. That's the equivalent of:

((?:(?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\"))))
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Alternatively, you can take the first regex above and just change the non-capturing group (?:...) that surrounds the entire expression into a capturing group:

((?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))
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Or, since you said you wanted to capture the stuff between the quotes, change that non-capturing group into a capturing one:

(?:(?|(?:\")([^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))
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Plus, there's a bunch of simplifications that could be made to the first regex above anyway (really just removing unnecessary groups):

/ \" [^\\\"]* (?: \\. [^\\\"]* )* \" /x
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and just add capturing groups to that as needed.

Ahh - I did not pay attention that you introducded a new capturing group by puttting the regex into an extra pair of brackets.

Now it all makes sense - many thanks.

I've never used Regexp::Common before but it seems to contain useful stuff - I see a bright future for it in my Go-Programs :-)