You are absolutely right! But, rereading the question, the whitespace and the dog aren't necessary, either. zer just asked for a regex that matches a string which does not begin with cat. So, I think /^(?!cat)/ should do it. That would match any line with a beginning which is not followed by a cat, right? 
--
-- GhodMode
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In reply to Re^3: Regex negative word by GhodMode
in thread Regex negative word by zer

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