使用标量作为perl中的条件 [英] Using a scalar as a condition in perl

问题描述

第一个计时器......所以，如果有任何我在提出问题时没有注意的话，请告诉我。

First timer...so let me know if there is anything that I have not paid attention to whilst posing a question.

问题是如何使用标量作为条件，因为下面的代码不起作用。

The question is how to use a scalar as a condition, as the code below does not work.

my @parameter=('hub');

my %condition;
$condition{'hub'}{'1'}='$degree>=5';

foreach (@parameter) {
       if ($condition{$_}{'1'}) {..}
}

我认为这是因为条件没有被正确解释，所以我也尝试了以下，但也没有用。

I thought that is because the condition is not interpreted correctly, so I also tried the following, which also did not work.

if ("$condition{$parameter}{'1'}") { ..}

非常感谢任何帮助。 :)

Would really appreciate any help. :)

推荐答案

您要么需要字符串eval，它将字符串计算为Perl代码

You either want string eval, which evaluates a string as Perl code

if (eval $condition{$_}{'1'}) { ...

或者更安全的方法是使用代码参考

or perhaps a more secure approach would be using code references

$condition{'hub'}{'1'} = sub { return $degree>=5 };

if ($condition{$_}{'1'}->()) { ...

在第二个示例中，您将一段代码附加到变量。 $ var->（）语法执行代码并计算代码的返回值。

In the second example, you are attaching a piece of code to a variable. The $var->() syntax executes the code and evaluates to the return value of the code.

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