When I read your post, I guess you mean "Exported data from Excel files", as .txt is something completely different.

Perl has an excellent module to parse native Excel files, it is called Spreadsheet::ParseExcel. If the API is too difficult (for you), you could consider the wrapper module Spreadsheet::Read, which uses Spreadsheet::ParseExcel under the hood. With both you can be the one controlling what and how you deal with the data in the spreadsheet(s).

Excel uses a binary format that is very portable across architectures, making it relatively easy to read those files on Windows as well as on AIX, HP-UX, MacOSX, etc etc.