Even if you got that regexp right from the start (you didn't, see the subthread with Abigail for why), you've been using that's considered a big no-no: (excerpt) 
      (?:       # Match stuff that isn't a closing delim:
        [^%]+     # Things that can't start one.
      | %+[^>]    # Might start one but isn't one.
      )*

[download]
You're using the dreaded /(A+|B+)*/, a star on top of a plus. That's considered very bad for regexps, because if the pattern fails for some reason, you'll get lots of unnecessary backtracking. Jeffrey Friedl also discusses this in his book "Mastering Regular Expressions", Chapter 5 p.144 in the 1st edition (which is all I have) under the subtitle "Reality Check".

For it to behave properly, you should loose the plusses.

In reply to Re: Re^2: A NOT in regular expressions (why [^%>]?) by bart
in thread A NOT in regular expressions by Anonymous Monk

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