October 2022
Beginner to intermediate
390 pages
7h 5m
Chinese
Content preview from Perl语言入门（第8版）
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72
｜
第
4
章
出现在开头部分。你可以随意选择采用哪种风格。不管怎样，你都不需要对子程序进
行事先声明。子程序的定义是全局的，除非你使用一些强有力的技巧，否则不存在所
谓的私有子程序。假如你定义了两个重名的子程序，那么后面的子程序会覆盖掉前面
的那个。如果启用了警告功能，
Perl
会告诉你有子程序被重复定义。一般来说，重名
总归是不够妥当的做法，也会让程序维护员感到困惑。
我们不会深入讨论不同包内的同名子程序，但我们的另一本书
Intermediate
Perl
中会有说明。
正如你在之前的例子中看到的，你可以在子程序主体中使用任何全局变量。事实上
,
目前你见过的所有变量都是全局的。这就是说，你可以在你的程序的任何位置访问这
些变量。很多语言学的好事者可能会为此感到震惊，但
Perl
开发组很多年前就组织了
一众手持火把的愤青，把这些好事者赶出群。我们稍后会在“子程序中的私有变量”
一节中学到如何建立私有变量。
调用子程序
在任意表达式中，子程序名前加上
&
就表示调用这个子程序：
&marine; #
打印
Hello, sailor number 1!
&marine; #
打印
Hello, sailor number 2!
&marine; #
打印
Hello, sailor number 3!
&marine; #
打印
Hello, sailor number 4!
通常，我们称之为调用（
calling
）子程序。本章会陆续介绍其他调用子程序的方式。
返回值
子程序被调用时一定是作为表达式的某个部分，即使该表达式的求值结果不会被用 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.