writing to an Excel spreadsheet

• [[*Spreadsheet::WriteExcel]], [[*Spreadsheet::WriteExcelXML]], [[*Excel::Writer::XLSX]] — very highly recommended; all have a similar API
• you can actually create a spreadsheet in Excel, save it as .xml, and then modify that XML structure
• if you can include VBA in a spreadsheet, it's possible to have the VBA add extra formatting when the spreadsheet is opened [1]

reading from an Excel spreadsheet

• [[*Spreadsheet::ParseExcel]] or [[*Spreadsheet::XLSX]]