Here's a quick fix for you until you get around this problem. It produces correct results for those dotty filenames both under Windows XP (5.6.1 active perl) and Linux (RedHat 9, 5.6.1 as well).
my $f = ". .";
my $result = minuse ($f);
print "[$result]\n";
sub minuse { -f $_[0] || &minusd}
sub minusd {local *D; opendir (D, shift) && (close (D) || 1)}
Thank you very much, that works fine.
I have installed Build 510 in the meantime and tested -e using that release.
All dotty files exist in that build as well, but anyway, this fix is fine for now.