#!/usr/bin/perl -l
use strict;
use warnings;
use Date::Calc qw/Days_in_Month Day_of_Week/;

my @days_of_week = qw/Mon Tue Wed Thu Fri Sat Sun/;

for my $year (1 .. 2500) {

    my %days_of_month;

    for my $month_of_year(1 .. 12) {
        for my $day_of_month(1 .. Days_in_Month($year,$month_of_year)) {
            my $dow = Day_of_Week($year,$month_of_year,$day_of_month);
            # Day_of_Week uses a 1-based index, hence the --$dow
            $days_of_month{$day_of_month}{$days_of_week[--$dow]}++;
        }
    }

    for my $day_of_month (sort {$a <=> $b} keys %days_of_month) {
        next if scalar keys %{$days_of_month{$day_of_month}} == 7;
        my @missing_days;
        for (@days_of_week) {
            push (@missing_days, $_) if !defined $days_of_month{$day_of_month}{$_};
        }
        print "In $year, Day $day_of_month does not fall on ",
              join(", ", @missing_days);
    }
}