How to set the environment in perl

How to set the environment in perl

怎么设置环境变量在perl, 我现在用perl写个周期执行的程序, 但运行之前要设置一些环境变量, 请问各位大侠怎么设环境变量.
先谢了!
$ENV{'my_var'}="my_value";
thanks!