Well, you might think it shouldn't make much of a difference, but perl happens to disagree with you. I disagree with you too, but it's probably perl that you'll rather listen to. :)

You see, there's only one way it could match, but there are plenty of ways it can fail (as in "almost succeed"). And a regex engine has a tendency to try them all, it's apparently not yet smart enough to know it can't succeed. Looking at the regex 

/(?:[^"]+|"")*/

[download]
and the string "around", there's plenty of ways this could possibly match: 
(around)
(aroun)(d)
(arou)(nd)
(arou)(n)(d)
...

[download]
Each phrase between parens indicates a group as matched by the subpattern [^"]+, and all groups are matched as a whole by * — as you can see, there are many ways it can be split up.

If you use the "cut" operator, there's only one way this can match: 

(around)

[download]
So it makes sense to expect that using the cut operator might yield a significant speed boost.

But, without further ado, here's the benchmark, as run with perl 5.8.8: 

my $s = q("You spin me ""around"" and ""around"", ""round"", like a re
+cord, ""round"" and ""around"".);
use Benchmark 'cmpthese';
cmpthese(-3, { 
  cut => sub { return  $s =~ /"(?>[^"]+|"")*"(?!")/ },
  straight => sub { return  $s =~ /"(?:[^"]+|"")*"(?!")/ } 
});

[download]
Results (neither the figures, nor their ratios), are not always the same, so take with a grain of salt: 
            Rate straight      cut
straight  7579/s       --     -89%
cut      69921/s     823%       --

[download]
That's a factor of 9, that /(?>[^"]+|"")*/ is faster than /(?:[^"]+|"")*/, for this string, and that is definitely not insignificant.

In reply to Re^4: Help with Double Double Quotes regular expression (imprecise) by bart
in thread Help with Double Double Quotes regular expression by mattford63

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