#!/usr/bin/perl
use Benchmark;
my %map = map { $_ => $_ } 0..9;
# cd1 is from https://metacpan.org/pod/Algorithm::LUHN
sub cd1 {
  my @buf = reverse split //, shift;
  my $totalVal = 0;
  my $flip = 1;
  foreach my $c (@buf) {
    my $posVal = $map{$c};
    $posVal *= 2 unless $flip = !$flip;
    while ($posVal) {
      $totalVal += $posVal % 10;
      $posVal = int($posVal / 10);
    }
  }
  return (10 - $totalVal % 10) % 10;
}
# cd2 is from: https://github.com/bdlightner/luhn-implementation-Perl-
sub cd2 {
    my($number) = @_;
    my($i, $sum, $ch, $num, $twoup, $len);
    $len = length($number);
    $sum = 0;
    $twoup = 1;
    for ($i = $len - 1; $i >= 0; --$i) {
        $ch = substr($number, $i, 1);
        $num = unpack('c', $ch) - 0x30;
        $num += $num if ($twoup);
        $num = int($num / 10) + ($num % 10) if ($num > 9);
        $sum += $num;
        $twoup = (++$twoup) & 1;
    }
    $sum = 10 - ($sum % 10);
    $sum = 0 if ($sum == 10);
    return $sum;
}
# example use:
my @range=(401135000000000..401135000099999);
timethese(10, {
    'Algorithm::LUHN' => sub { for(@range){cd1($_)} },
    'bdlightner' => sub { for(@range){cd2($_)} },
});
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