While working on the migration path towards 5.8.1, I find myself constantly stumbling over minor problems that are causing big problems. For a while, I've been trying to figure out why this weird pseudo-hash which is being exported all over the place (aargh! Encapsulation is being violated for performance reasons) isn't behaving nicely. As it turns out, it's because Class::MethodMaker has been subclassed to implement chained mutators, but the actual implementation overrode a private method whose behavior has changed.
In the process of debugging, I've tried to run the code under both 5.6.1 and 5.8.1 and confess() a bunch of Data::Dumper'ed data -- only to discover that both Carp and Data::Dumper have had their output formatting altered enough to make diffs rather problematic.
I now have most of the code running, though. I just need to track down one program runs which fine under 5.6.1 and segfaults under 5.8.1