Have you looked at the status code and the content of your response?

my $res= $ua->request($req);

print $res->is_success ? "yay\n" : "error\n";
print sprintf "Status %d\n", $res->code;
print $res->decoded_content;
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Maybe the module is correct and you don't actually get JSON back, but an error message that starts with Can't connect to myurl....