Actually there is one very reliable way to detect these situations - a comprehensive test suite.

Your test suite should have a test (or several) written for each of the cases that should cause a failure. If this test suite was run before each release you would catch the error that this post references.

Writing a compehensive set of tests can be an intimidating task, but the amount of time it will save you in the long run is well worth it.

Here is an article describing perl best practices, it has 10 tips from Damian Conway's excellent Perl Best Practices book.