Class::DBI is quite a simple module really
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I think it's actually a quite complex module, it's perl's Object-to-Relational mapping module. Other language's OR libraries are discussed in books, for example, there are at least five books dedicated to Hibernate, which is java's OR. I'm always wondering why nobody writes a book about Class::DBI, it would help to raise perl to "enterprise" status, after all, OR sounds fancy and well educated.