August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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72
｜
第
4
章
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。如果启用了警告信息，
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
》会有说明。
正如你在之前的例子中看到的，你可以在子程序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，子程序名前加上与号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!
虽然这里称之为调用（
invocation
）子程序，但我们更习惯称之为呼叫（
call
）子程
序。本章会陆续介绍其他呼叫子程序的方式。
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 wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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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.