There is something in this thread:

http://nntp.x.perl.org/group/perl.perl5.changes/7155

Change 19185 by jhi@kosh on 2003/04/10 19:06:02
        Noted by Nat: -0 didn't work that well with Unicode.
...
+If you want to specify any Unicode character, use the hexadecimal
+format: C<-0xHHH...>, where the C<H> are valid hexadecimal digits.
+(This means that you cannot use the C<-x> with a directory name that
+consists of hexadecimal digits.)
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