On Fri, Jan 12, 2007 at 03:17:36PM -0600, Sam Martin wrote: > ". . . (?!) is a pattern that never matches anything, so when the > regex engine reaches it, it is forced to backtrack. " Aye, and that's the flaw I see in this scheme... Backtracking. Whenever the regex engine hits the unmatchable (part of) your regex, it will happily back up, be a little less greedy, and try again to find a match. This can be a very expensive process, especially if your unmatchable bit is preceded by (or includes) a .* or similar token. Isaac and Eric have the right idea: Don't use an unmatchable regex, use a flag that tells you not to run a regex at all. It'll be much faster. -- I would rather be exposed to the inconvenience attending too much Liberty than those attending too small degree of it. - Thomas Jefferson