我有一系列的哈希值：
my @questions = (
{"Why do you study here?" => "bla"},
{"What are your hobbies?" => "blabla"});
我尝试遍历它：
foreach (@questions) {
my $key = (keys $_)[0];
$content .= "\\section{$key}\n\n$_{$key}\n\n";
}
给我
在convert.pl第44行的串联（。）或字符串中使用未初始化的值。
错误从何而来？
Gilles已经解释了如何使用当前数据结构，但是我建议您完全使用其他数据结构：简单的哈希。
#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
my %answers = (
"Why do you study here?" => "bla",
"What are your hobbies?" => "blabla"
);
while (my ($question, $answer) = each %answers) {
say "Question: $question";
say "Answer: $answer";
}
Question: Why do you study here?
Answer: bla
Question: What are your hobbies?
Answer: blabla
我发现这比散列数组更容易使用，每个散列只包含一个键/值对。
如果要按特定（未排序）顺序遍历哈希，则有两个选项。简单的解决方案是按要访问的键顺序维护键数组：
# In the order you want to access them
my @questions = ("What are your hobbies?", "Why do you study here?");
my %answers;
@answers{@questions} = ("blabla", "bla");
foreach my $question (@questions) {
say "Question: $question";
say "Answer: $answers{$question}";
}
Question: What are your hobbies?
Answer: blabla
Question: Why do you study here?
Answer: bla
另一个选择是使用Tie :: IxHash（或更快的XS模块Tie :: Hash :: Indexed）以插入顺序访问密钥：
use Tie::IxHash;
tie my %answers, "Tie::IxHash";
%answers = (
"Why do you study here?" => "bla",
"What are your hobbies?" => "blabla"
);
while (my ($question, $answer) = each %answers) {
say "Question: $question";
say "Answer: $answer";
}
Question: Why do you study here?
Answer: bla
Question: What are your hobbies?
Answer: blabla
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