#!/usr/bin/perl -wl

    use strict;

    use Date::Calc 'Nth_Weekday_of_Month_Year';


    sub max_days_in_month {

        my $day   = $_[0]; # Monday  is 1
        my $month = $_[1]; # January is 1
        my $year  = $_[2];

        scalar grep {Nth_Weekday_of_Month_Year($year, $month, $day, $_)} 1..5;
    } 


    print "There are ", max_days_in_month(1, 6, 2002), " Mondays in June 2002.";
    print "There are ", max_days_in_month(6, 6, 2002), " Sundays in June 2002.";

    __END__
    Prints:

    There are 4 Mondays in June 2002.
    There are 5 Sundays in June 2002.

    (Good news for those for prefer Sundays to Mondays)