Hi This code is from a book I am learning from: 
$sub{$dir}{CALLBACK} = $callback;

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I can see that the value corresponding the key held in the $dir variable in the hash called sub is a reference to another hash and that we are dereferencing it and adding the value of the variable $callback to its CALLBACK key. But why is the key CALLBACK in captials and unquoted. I have not seen this before. Many thanks

In reply to beginner question - why is hash key unquoted and in capitals by Anonymous Monk

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