Delayed String Interpolation - Try #2

raw = 'PARAM1 = #{param_1}, PARAM2 = #{param_2}'
params = { :param_1 => "foo", :param_2 => "bar" }

query = proc do |*args| 
  @params = params
  def method_missing(key)
    @params[key.to_sym]
  end
  eval('"' + raw + '"') 
end

puts query.call(params)