perl - 哈希参考中的 Perl 访问值

Question

在我的 Perl 代码中，我最终得到了如下所示的哈希引用。我想从中访问单个元素。我尝试了多种方法，但我无法获取它。

#!/usr/bin/perl
#use strict;
use Data::Dumper;
my %h={'one'=>1,'two'=>2};
print Dumper($h{'one'});

输出

$VAR1 = undef;

Answer 1

使用括号来构造您的哈希，而不是大括号：

use strict;
use warnings;
use Data::Dumper;

my %h = ('one'=>1, 'two'=>2);
print Dumper($h{'one'});

大括号用于构造散列引用。

另外， add use warnings;，它会生成一条消息，表明您的代码存在问题。

---

或者，如果你真的想要一个 hashref：

my $h = {'one'=>1, 'two'=>2};
print "$h->{one}\n";

Answer 2

What you've (accidentally) done there, is to create a hash with a key that is a stringified hash reference and a value that is undef. And perldoc perlref has a section called WARNING: Don't use references as hash keys.