in reply to
Reading in merged cells from Excel XLSX
Spreadsheet::XLSX is kinda unmaintained. Sadly, so is the alternative Spreadsheet::ReadSXC. Though imho the alternative shows better conformance to Spreadsheet::ParseExcel than the first one does.
The author of Spreadsheet::ParseExcel has plans to write Spreadsheet-ParseExcelXML for XLSX, but that is delayed because of Spreadsheet-WriteExcelXML iirc.
You could try to draw the author's attention by commenting on this ticket, preferably with a patch to make the module do what you want conforming to the behavior in Spreadsheet::ParseExcel.
Enjoy, Have FUN! H.Merijn