$content = $ua->request($req);

  my $data = $xml->XMLin($content);
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This is a bug. $content in this context is an HTTP::Response object, not something which can be blindly passed to XMLin() successfully. You first need to extract the XML from it. eg. by using decoded_content. I'd therefore refrain from calling the response $content in the first place.

Try replacing those two lines with:

my $response = $ua->request ($req);
my $content = $response->decoded_content;
my $data = $xml->XMLin ($content);
[download]

That ought to get you a little bit farther along at least.