in reply to Production Environments and "Foreign" Code
I cannot speak to your first question, however I can say that my experience with CPAN modules has been consistently positive and satisfying. Moreover, in cases where I've encountered problems or shortcomings, I've found the support from the Perl and OSS communities to be superior to anything offered by proprietary software companies. And of course the availability of the source means that modification/extension of the downloaded software is a feasible task.
Your employers need to be aware that utilizing a CPAN module in no way means that they won't have good support, or even local support. Almost certainly you'd be better off grokking and being the local goto guy for the local installation of a prewritten e.g., XML module than writing one from scratch and handling all of the design, development, and debugging yourself.