--------------------
20,000

          Rate substr3    s/// substr4
substr3 1.61/s      --    -93%    -96%
s///    23.1/s   1336%      --    -44%
substr4 41.2/s   2460%     78%      --

--------------------
40,000

           Rate substr3    s/// substr4
substr3 0.884/s      --    -96%    -98%
s///     23.1/s   2509%      --    -45%
substr4  41.6/s   4606%     80%      --

--------------------
80,000

           Rate substr3    s/// substr4
substr3 0.445/s      --    -98%    -99%  (warning: unreliable count)
s///     23.4/s   5162%      --    -42%
substr4  40.1/s   8897%     71%      --