ruby-2.1.0-preview1 changes in code samples.

gistfile1.rb

# def foo now returns a symbol instead of nil, allowing for something like this

class Thing
  protected def some;end
  protected def like; end
  def it; end
  protected def hot; end
end

Thing.new.protected_methods
=> [:some, :like, :hot]

# Refinements, example from [here](http://www.rubyinside.com/ruby-refinements-an-overview-of-a-new-proposed-ruby-feature-3978.html)

module TimeExtensions
  refine Fixnum do
    def minutes; self * 60; end
  end
end

class MyApp
  using TimeExtensions

  def initialize
    p 2.minutes
  end
end

MyApp.new    # => 120
p 2.minutes  # => NoMethodError

# F suffix will make `String` frozen.

"bla"f.gsub!("l", "k")
# RuntimeError: can't modify frozen String

# Complete list [here](https://github.com/ruby/ruby/blob/v2_1_0_preview1/NEWS)

"bla"f really looks like a syntax error to me

Had the exact same feeling.

Much better list here: http://rkh.im/ruby-2.1