Once upon a time, about 4/5 years ago, I was given a corrupted Ms excel file by a desperate girl who had just lost months of work.

I tried anything to resurrect that file, even opening it with newer or older excel versions, changing random bytes in it (!), replacing parts of it from a good xls file. None of it worked.

By that time, being a good guy :-), I already knew that Spreadsheet::ParseExcel and Spreadsheet::WriteExcel were on CPAN. Probably I could use those modules to try parsing the corrupted xls and writing it back to a new file.

That was what I did, and with a five lines perl script I saved that person's work.