C:\test\perl-5.14.0-RC1>perl
use Benchmark qw[ cmpthese ];;
print $];;
$str = '123456789';
cmpthese -10, {
 a=>q[ my ($a,$b) = $str =~  m/(23)[^8]+(8)/g; ],
 b=>q[ my ($a,$b) = $str =~  m/(23)[^8]+(8)/; ],
 c=>q[ my ($a) = $str =~  m/(23)/g ],
 d=>q[ my ($a) = $str =~  m/(23)/; ],
};;
^Z
5.014000      Rate    b    a    d    c
b 357543/s   -- -15% -33% -45%
a 422192/s  18%   -- -21% -35%
d 535621/s  50%  27%   -- -18%
c 653518/s  83%  55%  22%   --