sub is_leap_year {
    my $year = shift;

    if($year%100 == 0) {
        return 1 if $year%400 == 0;
    }
    else{
            return 1 if($year%4 == 0);
    }
    return undef;
}

##</code><code>##

$today = localtime;

sleep(-86400);

$yesterday = localtime;

print "Yesterday's date was $yesterday\n";