- Now the default values of keyword arguments can be omitted. Those 'required keyword arguments" need giving explicitly at the call time.
- Added suffixes for integer and float literals: 'r', 'i', and 'ri'.
- def-expr now returns the symbol of its name instead of nil.
- rb_profile_frames() added. Provides low-cost access to the current ruby stack for callstack profiling.
- introduced the generational GC a.k.a RGenGC (PDF).
Today marks the release of Ruby version 2.1.0. A brief list of changes since 2.0.0 has been posted, and file downloads are available. Here are some of the changes: