Spreadsheet::read is a perl module that tries to transparently read arbitrary spreadsheet files and return its content in a universal manner independent of the parsing module that does the actual spreadsheet scanning.

for microsoft excel, this module uses spreadsheet::xlsx (for newer files; see the libspreadsheet-xlsx-perl package) or spreadsheet::parseexcel (available in libspreadsheet-parseexcel-perl)

for comma-separated value (csv) files, this module uses text::csv (either the pure perl version in libtext-csv-perl, or, if available, the xs-accelerated version packaged as libtext-csv-xs-perl).

for squirrelcalc, there is a very simplistic built-in parser.