First, your $VAR1 is a reference to a hash with only one key, so

$VAR1->{ETPT}
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is needed. This one is another reference to another hash with only the key 'SERVER', so

$VAR1->{ETPT}{SERVER}
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Now, this is a reference to an array. You want to get all responses...

$VAR1->{ETPT}{SERVER}[0]{RESPONSE}    # First element of the array
$VAR1->{ETPT}{SERVER}[1]{RESPONSE}    # Second element of the array
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Probably you want to go for each element of the array like this:

for (@{$VAR1->{ETPT}{SERVER}}) {
   # here $_->{RESPONSE} is each response of the array
}
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Hope this helps.