Yes, same computer. I just reran the tests (3 times each, one after the other), and got the same results as before:
>c:\progs\perl588\bin\perl 674979.pl
Rate class_nodot class literal
class_nodot 3037/s -- -24% -100%
class 4008/s 32% -- -100%
literal 859954/s 28218% 21354% --
>c:\progs\perl588\bin\perl 674979.pl
Rate class_nodot class literal
class_nodot 3041/s -- -26% -100%
class 4087/s 34% -- -100%
literal 868745/s 28464% 21158% --
>c:\progs\perl588\bin\perl 674979.pl
Rate class_nodot class literal
class_nodot 3041/s -- -26% -100%
class 4117/s 35% -- -100%
literal 834248/s 27329% 20162% --
>c:\progs\perl5100\bin\perl 674979.pl
Rate class_nodot literal class
class_nodot 667282/s -- -10% -11%
literal 741037/s 11% -- -1%
class 747754/s 12% 1% --
>c:\progs\perl5100\bin\perl 674979.pl
Rate class_nodot literal class
class_nodot 667704/s -- -10% -12%
literal 742924/s 11% -- -2%
class 758776/s 14% 2% --
>c:\progs\perl5100\bin\perl 674979.pl
Rate class_nodot literal class
class_nodot 657342/s -- -11% -14%
literal 740217/s 13% -- -3%
class 766213/s 17% 4% --
So yes, something is slower. Not necessarily the regexp, but it's likely.