Bug aside, your regex could use some refactoring. I'd suggest: 
m{
  ( [^']*? (?: '[^']*' [^']*? )* )
  XX
  |
  (.+) $
}x

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The unrolled loop of the first half and the $ anchor of the second half should control the performance.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re^3: This regex seems to have splattered non-greedy everywhere by japhy
in thread This regex seems to have splattered non-greedy everywhere by fizbin

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