check_barcode.pl

#!/usr/bin/perl

use strict; use warnings;

while (<>) {
    chomp;
    my $bc = $_;
    $bc =~ s/"//g;
    next if (length($bc) != 14);
    next if ($bc !~ m/^1\d+$/);
    print "barcode: ", $bc, " ... ";
    if (&is_luhn_valid($bc)) {
        print "is luhn valid.\n";
    } else {
        print "NOT luhn valid!\n";
    }
}

sub is_luhn_valid {
    my ($number, $sum, $even) = (shift, 0, 0);
    for my $digit ( reverse split //, $number ) {
        $sum += $_ for split //, $digit * (1 + $even);
        $even = not $even;
    }
    return $sum % 10 == 0;
}