Item 90. Don’t require more than you need to use in your methods

Even if you are using good dependency injection (Item 89), keep the number of dependencies that you actually need to a minimum. Any more than a couple of dependencies will start to drive you insane and make your code unmaintainable.

Consider a module that checks your car’s license to ensure that it hasn’t expired. Maybe this Perl code lives in one of those automated cameras on traffic signals. The module doesn’t represent the automobile itself, but it can use an automobile object to access the license information: