Also, use $^E (Windows's GetLastError), not $! (C's errno).

>perl -MWin32::LongPath -E"renameL('a','b') or die qq{renameL: $!\n}"
renameL:

>perl -MWin32::LongPath -E"renameL('a','b') or die qq{renameL: $^E\n}"
renameL: The system cannot find the file specified
[download]