You are mistaken in your assumption that the observed lookahead-behavior would be incorrect. Both the “+” and the “{2,}” are as greedy as they are outside of lookaheads, but the lookahead matches repeatedly because it doesn't consume any characters by itself.

Let's play the manual regex engine game:

""."string-N-U-M-B-E-R-O-N-E" MATCH($1="string-N-U-M-B-E-R-O-N-")
"%s"."tring-N-U-M-B-E-R-O-N-E"  MATCH($1="tring-N-U-M-B-E-R-O-N-")
"%s%t"."ring-N-U-M-B-E-R-O-N-E"  MATCH($1="ring-N-U-M-B-E-R-O-N-")
"%s%t%r"."ing-N-U-M-B-E-R-O-N-E"  MATCH($1="ing-N-U-M-B-E-R-O-N-")
"%s%t%r%i"."ng-N-U-M-B-E-R-O-N-E"  MATCH($1="ng-N-U-M-B-E-R-O-N-")
"%s%t%r%i%n"."g-N-U-M-B-E-R-O-N-E"  MATCH($1="g-N-U-M-B-E-R-O-N-")
"%s%t%r%i%n%g"."-N-U-M-B-E-R-O-N-E"  MATCH($1="-N-U-M-B-E-R-O-N-")
"%s%t%r%i%n%g%-"."N-U-M-B-E-R-O-N-E"  MATCH($1="N-U-M-B-E-R-O-N-")
"%s%t%r%i%n%g%-%N"."-U-M-B-E-R-O-N-E"  MATCH($1="-U-M-B-E-R-O-N-")
...
"%s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%E%-%R"."-O-N-E"  MATCH("-O-N-E")
"%s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%E%-%R%-"."O-N-E"  FAIL
"%s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%E%-%R%-O-N-E".""  FAIL

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In reply to Re: look-ahead greed changed between perl releases? by amon
in thread look-ahead greed changed between perl releases? by raygun

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