use Benchmark;

    my $qr_regex  = qr/ab{1,}c{1,}/;
    my $str_regex =   "ab{1,}c{1,}";

    my $string = "asdabdabc";

    timethese(10000000, {
      'string'   => sub { $string =~ /$str_regex/  },
      'string/o' => sub { $string =~ /$str_regex/o },
      'qr'       => sub { $string =~ /$qr_regex/   },
           });