class PathExpander

def process_args
  pos_files = []
  neg_files = []
  flags     = []
  clean     = true
  args.each do |arg|
    case arg
    when /^@(.*)/ then # push back on, so they can have dirs/-/@ as well
      clean = false
      args.concat process_file $1
    when "-" then
      pos_files << arg
    when /^-(.*)/ then
      if File.exist? $1 then
        clean = false
        neg_files += expand_dirs_to_files($1)
      else
        flags << arg
      end
    else
      root_path = File.expand_path(arg) == "/" # eg: -n /./
      if File.exist? arg and not root_path then
        clean = false
        pos_files += expand_dirs_to_files(arg)
      else
        flags << arg
      end
    end
  end
  files = pos_files - neg_files
  files += expand_dirs_to_files(self.path) if files.empty? && clean
  [files, flags]
end