encode_utf8 把字符编码成字节 decode_utf8解码UTF-8到字符

   encode_utf8
      $octets = encode_utf8($string);

    Equivalent to "$octets = encode("utf8", $string)". The characters in
    $string are encoded in Perl's internal format, and the result is returned
    as a sequence of octets. Because all possible characters in Perl have a
    (loose, not strict) UTF-8 representation, this function cannot fail.

	等价于 "$octets = encode("utf8", $string)".  这个$string里的字符是编码成Perl内部的格式,

	结果是返回一个有序的八位字节。 因为所有的字符在Perl有一个(非正式的,不是严格的)表示,这个函数不能失败

	encode_utf8 把字符编码成字节

   decode_utf8
      $string = decode_utf8($octets [, CHECK]);

    Equivalent to "$string = decode("utf8", $octets [, CHECK])". The sequence
    of octets represented by $octets is decoded from UTF-8 into a sequence of
    logical characters. Because not all sequences of octets are valid UTF-8,
    it is quite possible for this function to fail. For CHECK, see "Handling
    Malformed Data".

	等价于
	"$string = decode("utf8", $octets [, CHECK])".

	有序的八位字节 通过 $octets 表示被解码从 UTF-8 到一个有序的逻辑字符。

	因为不是所有的有序的八位字节 是正确的UTF-8

	解码UTF-8到字符