Until you got to deploy it on a new, supported linux OS, and realize that CPAN modules that load are different that the old server, and the developers own works

Until you got to deploy it on a new, supported linux OS, and realize that CPAN modules that load are different that the old server, and the developers own workstation, and now things go to hell, but they worked great on the developers machine. (not just perl, python and others can be fun too). As an admin, not a dev, I appreciate the additional complexity and security concerns, but I much more appreciate the portability and reproducability.