Your post and your follow-up regarding your testing methodology suggest IO::Socket may be a bit lacking in tests of its own. In a perfect world, it would be loaded with tests that would tell you right away if your proposed change broke things.

The IO modules are on the Phalanx 100, so some additional tests might be welcome. Now I'm sure this would be biting off much more than you bargained for, but what about adopting the module and becoming a hoplite? Even if you're not up for that, it would be helpful to convert the test cases you came up with into module tests and submit them with your patch.