use Benchmark;

print "holli\n";
timethis (999999, sub { $_ = "fox comes and fox goes into forest"; s/(fox.+)(fox.+?forest)/${1}the $2/; });
print "borisz\n";
timethis (999999, sub { $_ = "fox comes and fox goes into forest"; s/(.*)(fox.+?forest)/$1the $2/; });
print "sh1tn\n";
timethis (999999, sub { $_ = "fox comes and fox goes into forest"; s/(?<=fox)(.+?)(fox)/$1the $2/; });
print "Roy Jonhson\n";
timethis (999999, sub { $_ = "fox comes and fox goes into forest"; s/(?=fox(?:(?!.*fox).)*forest)/the /; });