use Benchmark(cmpthese);
cmpthese(100_000, {
	'a' => sub {
		$_ = 'this that this those this these.';
		$a = () = /this/g;
	},
	'b' => sub {
		$_ = 'this that this those this these.';
		$a++ while(s/this//);
	}
});

##</code><code>##

      Rate   a   b
a 458716/s  -- -7%
b 492611/s  7%  --