I've never really bothered with raw HTTP responses, but I do happen to know that the header and body of any HTTP message (be it request or response) are separated by an empty line. There are probably modules to do what you want, but it can't be that difficult anyway.

$xml_resp = $response->as_string;
$xml_resp =~ s/^.+?\n\n//;           # this should do the trick.
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