Example refinement usage for alex`` in the #ruby channel on freenode.net

hash_slice_backport.rb

module HashSliceBackport
  refine Hash do
    def slice *keys
      keys.each_with_object({}) do |key, hash|
        hash[key] = self[key] if key?(key)
      end
    end
  end
end

class Node
  using HashSliceBackport

  def example
    {a: 100, b: 200, c: 300}.slice(:b, :a)
  end
end

Node.new.example
#=> {:b=>200, :a=>100}