スゲい簡単なPerl入門 -3rdDay ref: http://qiita.com/items/50ec171292de95e8ff3c

date.pm

package main;
my $date = main->new;
# Using Object(= Reference related with Package name) call subroutine in package
$date->set_date(9);
print "\n";
sub new {
        my $pkg = shift;
        bless {
                year    => undef,
                month   => undef,
                day     => undef,
                second  => undef
        },$pkg;
}
sub set_date {
        # this $self is for receiving 1st argument(in this case, $date)
        my $self = shift;
        my $time_dereference = shift;
        ($self->{year},$self->{month},$self->{day},$self->{hour},$self->{minute},$self->{second}) = ( gmtime time + $time_dereference * 3600 )[5,4,3,2,1];
        $self->{year} += 1900;
        $self->{month}++;
}
sub get_year {
        my $self = shift;
        return $self->{year};
}
sub get_month {
        my $self = shift;
        return $self->{month};
}
sub get_day {
        my $self = shift;
        return $self->{day};
}
sub get_hour {
        return $date->{hour};
}
sub get_minute {
        return $date->{minute};
}
sub get_second {
        return $date->{second};
}

file1.txt

$date->set_date(9);