I don't think that that solution gives the same results.

From perlre:

(?!pattern)
A zero-width negative lookahead assertion. For example /foo(?!bar)/ matches any occurrence of ``foo'' that isn't followed by ``bar''. Note however that lookahead and lookbehind are NOT the same thing. You cannot use this for lookbehind.

Perhaps you mean to use the (?<!pattern) look behind assertion?

More From perlre:

(?<!pattern)
A zero-width negative lookbehind assertion. For example /(?<!bar)foo/ matches any occurrence of ``foo'' that isn't following ``bar''. Works only for fixed-width lookbehind.

-Ben Jacobs (dooberwah)
http://dooberwah.perlmonk.org
"one thing i can tell you is you got to be free"

In reply to (dooberwah) I'm don't think that gives the same results by dooberwah
in thread Regular Expression Tweaking by dooberwah

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