Perl 中的模式匹配是如何工作的? [英] How does pattern matching work in Perl?

问题描述

我想知道模式匹配在 Perl 中是如何工作的.

I want to know how pattern matching works in Perl.

我的代码是:

my $var = "VP KDC T. 20, pgcet. 5, Ch. 415, Refs %50 Annos";

if($var =~ m/(.*)\,(.*)/sgi)
{
    print "$1\n$2";
}

我了解到应该匹配第一次出现的逗号.但这里最后一次匹配.我得到的输出是:

I learnt that the first occurrence of comma should be matched. but here the last occurrence is being matched. The output I got is:

VP KDC T. 20, pgcet. 5, Ch. 415
 Refs %50 Annos

有人可以解释一下这种匹配是如何工作的吗?

Can someone please explain me how this matching works?

推荐答案

来自 docs:

默认情况下，量化的子模式是贪婪的"，也就是说，它会尽可能多地匹配(给定一个特定的起始位置)，同时仍然允许模式的其余部分匹配

By default, a quantified subpattern is "greedy", that is, it will match as many times as possible (given a particular starting location) while still allowing the rest of the pattern to match

所以，首先 (.*) 会尽可能多.

So, first (.*) will take as much as possible.

简单的解决方法是使用非贪婪量词:*?.或者不匹配每个字符，但匹配除逗号之外的所有字符:([^,]*).

Simple workaround is using non-greedy quantifier: *?. Or match not every character, but all except comma: ([^,]*).

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