Symlinked directories can prevent the ignore functionality from working.
If you have a Library in a symlinked directory and you tell Devel::Cover
to ignore the symlinked directory, when it compares any file in that
symlinked directory against the ignore list the comparison fails since
it gets the absolute path of the file.
This can happen on user defined ignores using +ignore, or on the
compiled-in defaults if a user happens to have symlinks in their perl
configuration.
I've marked this unimportant since I imagine this is very rarely an
issue for anyone.