I think the problem is not your code, but rather an interaction between Perl 5.8.1 and Apache::Session. When your CGI ends, Perl tries to destroy all the objects. Some of the Apache::Session objects have DESTROY methods that get triggered when this happens. In Perl 5.8.1, you can no longer count on the order in which these get called, and I think that somehow the object holding the database handle is getting destroyed before another object that wants to use it. One way to find out would be to go into the A::S source code and add warning messages to all the DESTROY methods so you can see what order they get called in.

Unfortunately, the simplest fix for you would probably be to go back to 5.6.1. It has better performance anyway, so it might be a better choice. The only reasons to use 5.8.x are unicode and threads.