August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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用正则表达式进行匹配
｜
155
在这里例子里，根据
Perl
处理
$_
中字符串以及模式匹配中字符串的方式不同，你可
能会得到不同的结果。如果程序源代码用
UTF-8
保存，但输入的字符串是
Latin-9
编
码的，会发生什么？在
Latin-9
里面，字符
Œ
的内部编码为
0xBC
，而它的小写版
本
œ
的内部编码为
0xBD
。在
Unicode
里面，
Œ
的代码点是
U+0152
，而
œ
的代码
点是
U+0153
。在
Unicode
里，
U+0OBC
表示
¼
，它并没有什么小写版本。如果你
在
$_
中输入的是
0xBD
并且
Perl
将正则表达式作为
UTF-8
字符串来处理的话，是不
会得到预想的结果的。不过，你可以添加
/l
修饰符强制
Perl
按照本地化设定的规则
解析正则表达式的含义：
use v5.14;
my $OE = chr( 0xBC ); #
明确取得我们所讲的那个字符
$_ = <STDIN>;
if (/$OE/li) { #
好多了
print "Found $OE\n";
}
如果希望始终按
Unicode
语义阐释，做法同上面
Latin-1
的例子一样，在正则表达式
末尾明确写上
/u
修饰符：
use v5.14;
$_ = <STDIN>;
if (/Œ/ui) { #
现在使用
Unicode
print "Found Œ\n";
}
是不是觉得头很大？没错，谁都不喜欢这么复杂的情形，不过
Perl
在这里已经尽其所
能把该做的事都处理好了。要是能推倒历史重新来过的话，也许就不会闹出这么多麻 ...
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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.