Use of uninitialized value in subroutine entry at
I got this in the destruction in one of my objects when it tried to log its destruction.
Checking the Log4perl FAQ shows me that this means I have a circular reference somewhere in my code; Log4perl's getting called during global destruction, when the Log4perl structures have already been destroyed themselves.
Trying the easy and obvious thing first, I used Devel::Cycle and tried running it on the object that was being destroyed
I'm far too lazy to do that, so I thought about it a while. I had a small test case that duplicated the problem; how could I zero in on the point in the test case where I created the circular reference? The light came on: the debugger! I knew that Log4perl would throw its error during global destruction, so all I had to do was run through the code in the debugger, continuing to each point where I created more objects
In just a few minutes, I was able to zero in on the method that was creating the circular reference, and in just a minute more, to find exactly the piece of code that had created the problem. Toss in a weaken(), problem solved. I could have done this by editing the code and moving a exit through it, but this was simple and easy, plus I didn't have to change the code to find the problem.