gistfile1.rb

#!/usr/bin/env ruby

module StringRefine
  refine String do
    def refine_test
      self.upcase
    end
  end
end

class Hoge
  using StringRefine

  def test
    p 'hoge'.refine_test
    #=> "HOGE"

    p %w( hoge fuga ).map{|s| s.refine_test }
    #=> ["HOGE", "FUGA"]

    p %w( hoge fuga ).map(&:refine_test)
    #-> NoMethodError
  end
end

puts RUBY_VERSION
#=> 2.2.2

Hoge.new.test