C:\>perl5.6.1 p:\test\373536-2.pl
[SNIP]
        Rate Btest Atest Ctest Dtest
Btest 9.14/s    --   -0%   -3%   -3%
Atest 9.14/s    0%    --   -3%   -3%
Ctest 9.40/s    3%    3%    --   -0%
Dtest 9.42/s    3%    3%    0%    --

C:\>perl5.8.4 p:\test\373536-2.pl
      s/iter Btest Dtest Ctest Atest
Btest   4.23    --   -0%   -0%  -18%
Dtest   4.22    0%    --   -0%  -18%
Ctest   4.22    0%    0%    --  -18%
Atest   3.45   22%   22%   22%    --