正则表达式 $1 进入变量会干扰另一个变量 [英] Regex $1 into variable interferes with another variable

问题描述

我一直在努力处理我的一段代码，现在无法弄清楚.似乎与 $1 的处理方式有关，但我找不到任何相关内容.

I have been struggling with a section of my code for a while now and can't figure it out. Seems to have something to do with how $1 is handled but I cannot find anything relevant.

正则表达式找到 16640021 并将其分配给数组中的一个位置.

The regex finds the 16640021 and assigns it to a position in the arrays.

my @one;
my @two;
my $articleregex = qr/\s*\d*\/\s*\d*\|\s*(.*?)\|/p; # $1 = article number
my $row = "   7/  1|        16640021|Taats 3 IP10                       |14-03-03|        |    |        1,0000|st |   | 01|    | N|  0|";

    if ($row =~ /$articleregex/g) {
        $one[0] = $1; 
    }
    if ($row =~ /$articleregex/g) { 
        $two[0] = $1;
    }
print $one[0];
print $two[0];

哪些输出

Use of uninitialized value in print at perltest3.pl line 13.
16640021

$one[0] 的指定似乎在某种程度上干扰了 $two[0] 的指定.这对我来说似乎很奇怪，因为这两个变量及其名称不应以任何方式相互作用

It appears that the designation of $one[0] somehow interferes with that of $two[0]. This seems strange to me as the two variables and their designations should not be interacting in any way

推荐答案

这是因为你使用了 if (//g) 而不是 if (//).

It's because you used if (//g) instead of if (//).

• //g 在标量上下文中将 pos($_)^[1] 设置为匹配停止的位置，或取消设置 pos($_)^[1] 如果匹配不成功^[2].
• //g 在标量上下文中从位置 pos($_)^[1] 开始匹配.

• //g in scalar context sets pos($_)^[1] to where the match left off, or unsets pos($_)^[1] if the match was unsuccessful^[2].
• //g in scalar context starts matching at position pos($_)^[1].

例如

$_ = "ab";
say /(.)/g ? $1 : "no match";  # a
say /(.)/g ? $1 : "no match";  # b
say /(.)/g ? $1 : "no match";  # no match
say /(.)/g ? $1 : "no match";  # a

这允许以下内容遍历匹配项:

This allows the following to iterate through the matches:

while (/(.)/g) {
   say $1;
}

不要使用if (//g)^[3]！

1. $_ 用于表示匹配的变量.
2. 除非还使用了 /c.
3. 除非您正在展开 while (//g)，或者除非您使用 if (//gc) 进行标记化.

1. $_ is being used to represent the variable being matched against.
2. Unless /c is also used.
3. Unless you're unrolling a while (//g), or unless you're using if (//gc) to tokenize.

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