instance_eval_dsl.rb

module HttpClient
  class Dsl
    # These are the methods that your users are going to call
    def user_agent(agent)
      @user_agent = agent
    end

    def accept(accept)
      @accept = accept
    end

    # You can call this to get the data from the DSL object
    def params
      { accept: @accept, user_agent: @user_agent }
    end
  end

  def self.get(url, &definition)
    # Get a new "container" and pass it into a block
    dsl = Dsl.new
    dsl.instance_eval(&definition)
    # voila, now your properties are in the "dsl" variable!

    puts "GET #{url}"
    puts "User-Agent: #{dsl.params[:user_agent]}"
    puts "Accept: #{dsl.params[:accept]}"
  end
end

HttpClient.get('https://example.com') do
  user_agent "Ruby"
  accept "text/plain"
end