(                        group and capture to \1:
----------------------------------------------------------------------
    (                        group and capture to \2:
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      .                        any character except \n
----------------------------------------------------------------------
    )                        end of \2
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    \2                       what was matched by capture \2
----------------------------------------------------------------------
    \2                       what was matched by capture \2
----------------------------------------------------------------------
  )                        end of \1
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  \2*                      what was matched by capture \2 (0 or more
                           times (matching the most amount possible))