I find that I am not doing a very good job of being precise. The END block that failed to execute in my previous statement was the last line of the master script. I did also attempt a manual DEMOLISH (Moose) block at the end of all classes where all but the master class DEMOLISH executed correctly. The master class DEMOLISH failed repeatably for a very specific attribute clearance with some variations done in testing to validate that was the unclearable attribute. In order to understand if I had somehow triggered the DEMOLISH calls out of sequence I also deleted all class DEMOLISH blocks in order to see if perl's automatic garbage collection would fix the problem as well. Neither solution worked.