I have just released Class::MOP-0.01 to CPAN (appearing soon on a CPAN mirror near you). It attempts to create a complete meta-object protocol for Perl 5 and bring support for metaclass programming to Perl 5. Or course, this being a 0.01 release, there is still much that can be done and many improvements that can be made, but I feel it is a good start.
This is largely inspired by my work on the Perl 6 metamodel and my recent studies of CLOS, and as a side benefit, it is useful for my $work as well
Any questions, comments or criticisms are welcome.