use strict;
use warnings;
use Benchmark 'cmpthese';
cmpthese(
  -2,
  {
    holli => sub {
      $_ = "fox comes and fox goes into forest";
      s/(fox.+)?(fox.+?forest)/${1}the $2/;
    },
    Roy => sub {
      $_ = "fox comes and fox goes into forest";
      s/(?=fox(?:(?!fox).)*forest)/the /;
    },
    ikegami => sub {
      $_ = "fox comes and fox goes into forest";
      s/(fox(?:(?!fox).)*forest)/the $1/;
    },
    borisz => sub {
      $_ = reverse "fox comes and fox goes into forest";
      s/(tserof.*?)xof/${1}xof eht/;
      $_ = reverse;
    }
  }
);
__OUTPUT__
           Rate   holli ikegami     Roy  borisz
holli   62934/s      --     -3%    -25%    -31%
ikegami 65121/s      3%      --    -23%    -29%
Roy     84099/s     34%     29%      --     -8%
borisz  91530/s     45%     41%      9%      --