The CONCATENATE function has been treated as equivalent to CONCAT. This is not how it is treated in Excel; it is closer to (and probably identical to) the ampersand concatenate operator. The difference manifests itself when any of the arguments is an array (typically a cell range). Code is added to support this difference.
Support for array results is added to Csv Writer, Html Writer, and Ods Reader and Writer. I have not figured out how to get it to work with Xls.