bytes pragma problems

Has anyone noticed that a call to bytes::substr() sends perl into a 
seemingly infinite loop
under v5.8.1-RC3 built for darwin-thread-multi-2level?

        use bytes;
        print bytes::substr( "abc", 0, 1 );

I also noticed that a call to a non-existent bytes subroutine will 
cause an infinite loop under v5.8.2 built for i686-linux.
        use bytes;
        print bytes::twtowtdi()

Were these problems resolved in later releases of Perl?

//Ed