你如何在Perl中按合同设计？

# 定义合同类
package Contract;

sub new {
    my ($class, $customer, $product) = @_;
    my $self = {
        customer => $customer,
        product => $product,
    };
    bless $self, $class;
    return $self;
}

sub get_customer {
    my ($self) = @_;
    return $self->{customer};
}

sub get_product {
    my ($self) = @_;
    return $self->{product};
}

package main;

# 创建合同对象
my $contract = Contract->new("John Doe", "Software Development");

# 获取合同信息
print "Customer: " . $contract->get_customer() . "\n";
print "Product: " . $contract->get_product() . "\n";