SELECT xmlconcat('bad', '<syntax');
SELECT xmlconcat('<foo/>', NULL, '<?xml version="1.1" standalone="no"?><bar/>');
SELECT xmlconcat('<?xml version="1.1"?><foo/>', NULL, '<?xml version="1.1" standalone="no"?><bar/>');
SELECT xmlconcat('bad', '<syntax');
SELECT xmlconcat('<foo/>', NULL, '<?xml version="1.1" standalone="no"?><bar/>');
SELECT xmlconcat('<?xml version="1.1"?><foo/>', NULL, '<?xml version="1.1" standalone="no"?><bar/>');