Perl替换操作符的作用是什么?

I have been programming in Perl, off and on, for years now, although only sporadically is it my primary language. Because I often go months without writing any perl, I rely heavily on my dog-eared Camel Book to remind me how to do things. However, when I copy recipes verbatim with no understanding, this bothers me. This is one of the most vexing: On page 154 of the 3rd edition Camel, there is an example for "modifying strings I have been programming in Perl, off and on, fo