Overlapped IO is what Windows calls its asynchronous IO mechanism. It allows one to start an IO operation (say, read from the disk) in a non-blocking fashion. Once the operation is completed, an Event is raised letting the application known the transfer completed.

I don't know why you're seeing that in Perl. I'd consider it a bug.

I'd try to sleep a bit and try again. Repeat until the error changes to success or a "real" error.

By the way, keep in mind you should only check GetLastError if you were told a system error occured.