[求助]wide character

[求助]wide character
在运行PERL程序时，出现了以下警告，但是最后的结果是正确的，怎样处理后就没有那样的错误了，而且我也不太明白那个警告的意思，希望得到帮助，谢谢！
Wide character in print at C:\Perl\bin\ex1.pl line 17 (#1)
  (W utf8) Perl met a wide character (>255) when it wasn't expecting
  one. This warning is by default on for I/O (like print). The easiest
  way to quiet this warning is simply to add the :utf8 layer to the
  output, e.g. binmode STDOUT, ':utf8'. Another way to turn off the
  warning is to add no warnings 'utf8'; but that is often closer to
  cheating. In general, you are supposed to explicitly mark the
  filehandle with an encoding, see open and perlfunc/binmode.

加了一句--no warnings .
加了一句
no warnings "utf8"
就可以了，不过还不明白什么原因