From your question, I assume that you are a beginner in Perl. In this case, I recommend that you add use diagnostics; in addition to strict and warnings. It will give you more information about the messages.

%dns_check = ("address" => "ip");
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You should always "declare" your variables, to tell Perl whether you want to have a lexically scoped or a globally scoped variables. For the time being (until you get more experience), I suggest you use only lexically scoped variables. You declare it using my:

my %dns_check = ("address" => "ip");
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See my.