The same thing came up in Perl 6 development more times than I could remember. Someone would show up and say "I have a very basic Perl 6 implementation on $virtual_machine that's n times faster than $other_implementation!" and it turns out they had implemented a calculator which did integer math.
No disrespect to Flavio or Perlito, but "fast subset" only starts to get interesting when that "subset" is more set than sub.
... except for the things that make Perl 5 slow, like tie and overload and AUTOLOAD, and other things that real programs tend to rely on like CPAN and XS and timely destruction and variable aliasing and Unicode and BEGIN and caller context.
Like I said, "subset".
Again, I like Perlito and I want to see it succeed, but its current performance numbers demonstrate that the subset of Perl that isn't exceedingly difficult to optimize can be implemented with pretty good efficiency. That's all.