Testing the code before the update, I get:

Benchmark: timing 15000 iterations of Aristotle, Fatvamp, bobn...
 Aristotle:  3 wallclock secs ( 2.47 usr +  0.00 sys =  2.47 CPU) @ 60
+72.87/s (n=15000)
   Fatvamp:  3 wallclock secs ( 3.51 usr +  0.00 sys =  3.51 CPU) @ 42
+73.50/s (n=15000)
      bobn:  3 wallclock secs ( 2.35 usr +  0.00 sys =  2.35 CPU) @ 63
+82.98/s (n=15000)
            Rate   Fatvamp Aristotle      bobn
Fatvamp   4329/s        --      -29%      -33%
Aristotle 6098/s       41%        --       -5%
bobn      6452/s       49%        6%        --
[download]

But I think someone else has sicne posted code, using substr(), that beats us all.

--Bob Niederman, http://bob-n.com