perl-rename-apfs

=pod

I'm experiencing an odd problem on macOS 10.13. I suspect it's
something to do with APFS (Encrypted). It looks like there's some
other magic when I try to rename a file to a name that already exists.
I could not reproduce this on FAT or HFS+ filesystems.

I've tried this with perls back to 5.12, all compiled with clang
(4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)).

Start with a file named F<Changes> and no file named F<Changes.bak>.

=over 4

=item Run it the first time. You should end up with a F<Changes> and a F<Changes.bak>.

=item Run it again. You end up with F<Changes> and F<Changes 3> file. This is odd.

=item Run it again. You end up with a F<Changes> file, F<Changes.bak>, and F<Changes 3>.

=item Run it again. You end up with a F<Changes> file, F<Changes 3>, and F<Changes 4>.

=back

=cut

	my $changes = "Changes";
	my $bak     = $changes . ".bak";

	rename $changes, $bak or die "Could not backup $changes. $!\n";

	open my $in, '<', $bak or die "Could not read old $changes file! $!\n";
	open my $out, ">", $changes;

	print {$out} 'Hello';

	close $out;
	close $in;