I have a server that runs Debian, and recently when I did an apt-get upgrade, it upgraded perl from 5.8 to 5.10. What hadn't occurred to me was that I had some scripts that were still running, which had been initialized with @INC set to all the proper paths for 5.8. I didn't notice until several weeks later that they were crashing with errors whenever they were invoked. The solution was simply to restart the scripts. I have a list of tests that I always do after an upgrade, and now this is on my list. But is there some simpler/easier/graceful/automagic way to approach this? Another issue that creates hassles is that I use apt for all the perl modules that are packaged for debian, and cpan for the rest; sometimes apt and cpan step on each other's toes.
Thanks, everyone, for the replies! Wow, I really learned a lot from this discussion -- both about perl and about unix :-)