Not being an admin is not reason not to be able to use useful modules. Looking arounf here (use search) will popup a wealth of links describing how even you can use the wonders of CPAN without being a superuser.

For parsing xlsx, you will need Spreadsheet::ParseXLSX and not Spreadsheet::ParseExcel. The API is much alike.

The ssconvert program is so outdated, it doesn't know about xlsx. I could not find a version available for OpenSUSE to test with (and I'm not going to dig for sources and build from scratch).

For dumping xls, xlsx, ods, and csv to CSV, I'd suggest installing Spreadhseet::Read, which supports all underlying parsers and comes with the xls2csv script, which has a lot of options.