http://www.perlmonks.org?node_id=939659


in reply to Nested grouping or capturing inside capturing

Named back reference save your ($4 || $3), but I wonder this is elegant or not. 
print "$1-$2-$+{third}\n"
    if m/
      (\w+)\s
      (\w+)\s
      (?: "(?<third>[^"]+)" | (?<third>\w+))
    /x;

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