And, with ikegami's test code, run on Ubuntu with perl, v5.8.7 built for i486-linux-gnu-thread-multi (with 1 registered patch...), there's significant variation with variance of x:
our $line = ('a' x 5500) . ' ' . ('a' x 120);
ww@GIG:~/pl_test$ perl 674979.pl</p>
Rate class_nodot class literal
class_nodot 242/s -- -30% -100%
class 344/s 42% -- -100%
literal 106283/s 43872% 30824% --
whereas, with ikegami's original, our $line = ('a' x 500) . ' ' . ('a' x 20);
ww@GIG:~/pl_test$ perl 674979.pl
Rate class_nodot class literal
class_nodot 2647/s -- -30% -100%
class 3793/s 43% -- -99%
literal 672122/s 25292% 17620% --