当运行cpan时提示：
Sorry, we have to rerun the configuration dialog for CPAN.pm due to
some missing parameters... Will write to
<</home/chankey/.cpan/CPAN/MyConfig.pm>>
The following questions are intended to help you with the
configuration. The CPAN module needs a directory of its own to cache
important index files and maybe keep a temporary mirror of CPAN files.
This may be a site-wide or a personal directory.
然后cpan会让你设置参数 一直按回车 到最后输入一个cpan的镜像就好了（
http://mirrors.163.com/cpan/
）
输入完之后用下面的命令保存配置