Counting the number of black Fridays in years

black_fridays.pl

#!/usr/bin/env perl

use strict;
use warnings;
use feature ':5.10';
use DateTime;
use Text::Pluralize;

my @counts = ("");

for my $year (2000..12000) {
    my @black_fridays;
    for my $month (1..12) {
        push @black_fridays, "$year-$month-13"
            if DateTime->new(year => $year, month => $month, day => 13)->day_of_week == 5;
    }
    say pluralize(
        "%d black Friday(s) in the year $year: @black_fridays",
        @black_fridays
    );
    $counts[@black_fridays]++;
}

say "There are " . $counts[$_] ." $_-black-Friday years"
    for 1..3;