在用 Perl 编写 CGI 时，这曾经是一个非常标准的做法.甚至还有一个 FAQ. 基本思想是运行时可以保证你没有隐含地信任一个被污染的值.

It used to be a pretty standard practice when writing CGIs in Perl. There is even a FAQ on it. The basic idea was that the run time could guarantee that you did not implicitly trust a tainted value.