It's said that there are two great unsolved problems in computer science: naming, cache invalidation, and off-by-one errors.

If you have a text file and you need to point to particular lines of the file, you may be familiar with the off-by-one errors problem. That's where Text::LineNumber by Jurgen Wiegert comes to the rescue. With this module you no longer need to think about calculating line numbers, but can just hand off the work to the module.