"In constructing Klein, we have attempted to adhere to various principles, including object-orientation, metacircularity, heavy code reuse, reactiveness, and mirror-based reflection. We expect these principles to yield many benefits, including:

• A simpler, more malleable VM (because it is written almost entirely in a high-level language).
• Less replicated code (because the VM and the applications running on top of it are written in the same language and can share code, as can the VM and its development environment).
• Better performance (because the VM will be able to do optimizations across the entire code base, including the VM code itself - imagine being able to inline the hotspots of the VM right up into an application).
• Faster turnaround when making changes to the VM (because the VM will no longer be tied to C++ and its compilation system)."

http://kleinvm.sourceforge.net/

However, the current version is not complete yet as a lot of things are yet to be done.

Erick