It turns out that
qr// is actually the
worst way to build regexes, but adding
/o mostly fixes the problem.
use Benchmark qw( cmpthese );
print $], "\n";
open my $W, '<', '/usr/share/dict/words' or die;
my @words = <$W>;
close $W;
my $s = '(?<![cC])[eE][iI]';
my $re = qr/(?<![cC])[eE][iI]/;
cmpthese(-5, {
re => sub { grep /(?<![cC])[eE][iI]/, @words },
qr => sub { grep /$re/, @words },
qro => sub { grep /$re/o, @words },
s => sub { grep /$s/, @words },
so => sub { grep /$s/o, @words },
});
__END__
5.026001
Rate qr s qro so re
qr 7.14/s -- -57% -67% -68% -69%
s 16.8/s 135% -- -22% -26% -26%
qro 21.4/s 200% 28% -- -5% -6%
so 22.5/s 215% 34% 5% -- -1%
re 22.7/s 218% 36% 6% 1% --
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