Thanks, Dave, for the cogent explanation. That would explain why some testers are reporting the errors and others are not. Of course, that in turn raises the question: How can we encourage our testers to correct such problems?

As to what in my code is triggering the problem, the most likely candidate is File::Temp, which is used in all files in test suite except the first -- which is the one file that gets through all its tests. But the problem is probably not File::Temp per se but the IO::Handle which File::Temp calls internally.

I'm loathe to stop using a core module such as File::Temp in my test suite, particularly because part of the testing process is the creation of files and directories which ought to be done in a protected environment such as File::Temp provides. And what about folks who use File::Temp in their module code, not just in their test suites?

Thanks again for taking the time to think about this problem.

Jim Keenan