I believe that in those examples, Perl is actually leaking the scalars, along with a lot of other stuff -- look at the "still reachable" stat. It's doing this intentionally, by exiting immediately rather than painstakingly deallocating everything first.

The lesson to take was that there is no difference in the valgrind output between the two runs, which demonstrates that it can't detect the scalars that I leaked in the second run.