regex - 使用数组时的 Perl 模式匹配

Question

我在匹配模式时遇到了一个奇怪的问题。

考虑下面的 Perl 代码

#!/usr/bin/perl -w

use strict;
my @Array = ("Hello|World","Good|Day");

function();
function();
function();

sub function 
{
  foreach my $pattern (@Array)  
  {
    $pattern =~ /(\w+)\|(\w+)/g;
    print $1."\n";
  }
    print "\n";
}

__END__

我期望的输出应该是

HelloGoodHelloGoodHelloGood

---

But what I get is

HelloGoodUse of uninitialized value $1 in concatenation (.) or string at D:\perlfiles\problem.pl line 28.Use of uninitialized value $1 in concatenation (.) or string at D:\perlfiles\problem.pl line 28.HelloGood

What I observed was that the pattern matches alternatively.
Can someone explain me what is the problem regarding this code.
To fix this I changed the function subroutine to something like this:

sub function 
{
    my $string;
    foreach my $pattern (@Array)
    {
        $string .= $pattern."\n";
    }
    while ($string =~ m/(\w+)\|(\w+)/g)
    {
            print $1."\n";
    }
    print "\n";
}

现在我得到了预期的输出。

Answer 1

是全局/g正在工作的修饰符。它记住最后一个模式匹配的位置。当它到达字符串的末尾时，它会重新开始。

删除 /g修饰符，它将按照您的预期运行。