* Profile guided typing
  http://www.cs.umd.edu/~davidan/papers/druby-tr-4935.pdf
* proc/lambda
* Exceptions (raise/rescue)
* Struct
* callcc
* Recursive customization
* Integrate document server
* Scanf type inference
* Performance tuning
  * CPU usage
  * Memory footprint
  * Cloning template
  * Cut branches
  * Statistics
* stubs load-path
