Lightweight preference system for ruby

UPDATE:
I have replace this method with a yaml method

Original Post:
When using GUI applications it is often nice for them top remember some of the settings, here is some snippets of a preferences system:

Near start of ruby app/script
----

   outputFile = ".photoflow/.photoflowrc"

   #Define before opening so new variables are definde empty.
   #   If undefiened never get added to the config file,
   #   which is a pain for manual edits.
   @raw_conf_folder_loc = ""
   @drv_conf_folder_loc = ""

   #Loaded Prefs from file
   if File.exist?(outputFile)
      configfile = File.new(outputFile, "r")
      while (line = configfile.gets)
         eval("#{line}")
      end
      configfile.close
   end

----

When any of the user setting are changed call 'createConfig'
----

 def createConfig(outputFile, raw_conf_folder_loc, drv_conf_folder_loc)
    FileUtils.mkdir_p (".photoflow")
    ## Delete output File if It exists
    if File.exists?(outputFile)
       File.delete(outputFile)
    end

    outputFileHandler = File.new(outputFile, File::CREAT|File::WRONLY)
    outputFileHandler.puts("\@raw_conf_folder_loc = \"" + raw_conf_folder_loc + "\"")
    outputFileHandler.puts("\@drv_conf_folder_loc = \"" + drv_conf_folder_loc + "\"")
    return 
 end

----

I have some problem with the scope of the variables, ideally I would not need to pass them as arguments to the function.

NB: Ruby functions are contained in def's, ie def SomeFunction end