ex.

  ## create parser
  arg_none     = "hv"      # ex. -h -v
  arg_required = "xf"      # ex. -x suffix -f filename
  arg_optional = "i"       # ex. -i  (or -i10)
  parser = CommandOptionParser.new(arg_none, arg_required, arg_optional)

  ## parse options
  argv = %w[-h -v -f filename -i 10 aaa bbb]
  options, properties = parser.parse(argv)
  p options   #=> { ?h=>true, ?v=>true, ?f=>"filename", ?i=>true }
  p argv      #=> ["10", "aaa", "bbb"]

  ## parse options #2
  argv = %w[-hvx.txt -ffilename -i10 aaa bbb]
  options, properties = parser.parse(argv)
  p options   #=> { ?h=>true, ?v=>true, ?x=>".txt", ?f=>"filename", ?i=>10 }
  p argv      #=> ["aaa", "bbb"]

  ## parse properties
  argv = %w[-hi --index=10 --user-name=foo --help]
  options, properties = parser.parse(argv)
  p options     #=> {?h=>true, ?i=>true}
  p properties  #=> {"index"=>"10", "user-name"=>"foo", "help"=>nil}

  ## parse properties with auto-convert
  argv = %w[-hi --index=10 --user-name=foo --help]
  options, properties = parser.parse(argv, true)
  p options     #=> {?h=>true, ?i=>true}
  p properties  #=> {:index=>10, :user_name=>foo, :help=>true}

  ## -a: unknown option.
  argv = %w[-abc]
  begin
     options, properties = parser.parse(argv)
  rescue CommandOptionError => ex
     $stderr.puts ex.message     # -a: unknown option.
  end

  ## -f: argument required.
  argv = %w[-f]
  begin
     options, properties = parser.parse(argv)
  rescue CommandOptionError => ex
     $stderr.puts ex.message     # -f: argument required.
  end

  ## --@prop=10: invalid property.
  argv = %w[--@prop=10]
  begin
     options, properties = parser.parse(argv)
  rescue CommandOptionError => ex
     $stderr.puts ex.message     # --@prop=10: invalid property.
  end