http://www.ruby-lang.org/en/news/2013/02/08/ruby-2-0-0-rc2-is-released/
正式版也快了吧
Keyword arguments
Enumerable#lazy
Module#prepend
#to_h: Convention for conversion to Hash
%i: a literal for symbol array
Updated regexp engine: Onigmo (a fork of Oniguruma)
Enumerator#size and Range#size were introduced
DTrace support
TracePoint
Optimized require performance (especially, on Windows)
NativeClient support
Documentation improvement
Enhanced asynchronous interrupt handling
Launch-time stack size tuning parameters
Refinements [experimental]