refine_03.rb

module TemporaryPatch
  refine Hash do
    def to_s
      ''
    end
  end
end

my_ebook = {
  ebook:   'Ruby Object Model',
  url:     'https://goo.gl/87b1bi',
  message: 'feel free to have a look to my new project ;-)'
}

p my_ebook.to_s # => "{\"ebook\":\"Ruby Object Model\", ...}"

using TemporaryPatch

lolcat = { lol: 'cat' }

p lolcat.to_s   # => ""
p my_ebook.to_s # => ""