Source code in the perl programming language

use Benchmark;
use Memoize;

sub fac1 {
    my $n = shift;
    return $n == 0 ? 1 : $n * fac1($n - 1);
}
sub fac2 {
    my $n = shift;
    return $n == 0 ? 1 : $n * fac2($n - 1);
}
memoize('fac2');

my $result = timethese(100000, {
    'fac1' => sub { fac1(50) },
    'fac2' => sub { fac2(50) },
});
Benchmark::cmpthese($result);


sub cpu_time {
  my ($user,$system,$cuser,$csystem) = times;
  $user + $system
}

sub time_it {
  my $action = shift;
  my $startTime = cpu_time();
  $action->(@_);
  my $finishTime = cpu_time();
  $finishTime - $startTime
}

printf "Identity(4) takes %f seconds.\n", time_it(sub {@_}, 4);
# outputs "Identity(4) takes 0.000000 seconds."

sub sum {
  my $x = shift;
  foreach (0 .. 999999) {
    $x += $_;
  }
  $x
}

printf "Sum(4) takes %f seconds.\n", time_it(\&sum, 4);
# outputs "Sum(4) takes 0.280000 seconds."