I have downloaded the file for sec/edgar/filings/ interactive data view in excel

which is in both the format some are in xlsx and some in xls..

the files with .xlsx extention works well with the module spreadsheet::XLSX

but when the file is in .xls format i need to do parsing with Spredsheet::ParseExcel

that i know very well

bothe the file comes from same source then its obvious that both are in excel format and excel files .

then why i cant open the .xls file that is my question