use Benchmark(cmpthese);
cmpthese(1000000, {
	'a' => sub {
		$_ = '12-12-12-12-12';
		undef $h{$1} while (s/(\d\d)//);
	},
	'b' => sub {
		$_ = '12-12-12-12-12';
		undef $h{$1} while (m/(\d\d)/g);
	},
	'c' => sub {
		$_ = '12-12-12-12-12';
		undef @h{m/\d\d/g};
	}
});

##</code><code>##

      Rate    a    b    c
a 195427/s   -- -19% -35%
b 241896/s  24%   -- -20%
c 300933/s  54%  24%   --