ccard checksum

ccard_number_validation.pl

#!/usr/bin/perl

use common::sense;
use List::Util qw(sum);

my $ccard = shift;

print crunch($ccard) ? "OK" : "BAD", "\n";

sub crunch {
    my $skip   = 1;
    my @digits = reverse map { split m// } map {($skip=not $skip) ? $_*2 : $_} reverse split m//, shift;

    my $checksum = sum @digits;

    return !($checksum % 10);
}