curl ENDPOINT \
  -H "Authorization: Bearer ACCESS_TOKEN" -X POST \
  -F attributes='{"name":"test.txt", "parent":{"id":"0"}}' \
  -F file=@test.txt

##</code><code>##

my $json = encode_json {"name" => "test.txt", "parent" => {"id" => 0}};

my $resp = $ua->post(
            ENDPOINT , 
           {file => <$fh> ,'attributes'=>$json },
          'Authorization' => 'Bearer ' . $token ,
           Content_Type => 'multipart/form-data' .
  );