使用数组时的Perl模式匹配

I have a strange problem in matching a pattern.

我在匹配模式时遇到了一个奇怪的问题。

Consider the Perl code below

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__

The output I expect should be

我期望的输出应该是

Hello
Good

Hello
Good

Hello
Good

But what I get is

但我得到的是

Hello
Good

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

Hello
Good

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:

我观察到的是模式交替匹配。有人可以解释一下这段代码有什么问题。为了解决这个问题，我将函数子例程更改为：

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

Now I get the output as expected.

现在我按预期得到了输出。

1 个解决方案

#1

It is the global /g modifier that is at work. It remembers the position of the last pattern match. When it reaches the end of the string, it starts over.

它是全局/ g修饰符正在起作用。它记住了最后一次模式匹配的位置。当它到达字符串的末尾时，它会重新开始。

Remove the /g modifier, and it will act as you expect.

删除/ g修饰符，它将按预期运行。

#1