Nothing accidental about the negation of that character class. I'm using it with a negative look-behind assertion. It's supposed to mean: "If it's not true that the preceding character is not a linebreak". So it's either a linebreak or there's nothing there at all (beginning of string).

Processing a file approximately 0.5MB in size, using gettimeofday for timing, I get
First version: 0.7 seconds
Second version: 0.003 seconds
Third version: 0.03 seconds

My actual regexes are slightly more complicated than the examples given so I see little speed difference between #2 and #3.

In reply to Re^3: Inexplicably slow regex by Anonymous Monk
in thread Inexplicably slow regex by Anonymous Monk

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