1) There is no Spreadsheet
module at CPAN. There are 100s of other modules such as Spreadsheet::Perl, Spreadsheet::Read etc. which do the job. Check out http://search.cpan.org/search?query=...et%3B&mode=all
So, it maybe that you are using a non-standard module which is not present at CPAN.
2) The problem which you state, seems to be a result of inefficient coding, rather than a module bug (I may be wrong though). You need to post the code which you are using and also the module (or a link to it), so that we can try to review and see where lies the problem.
In the meantime, you may try to optimize your code by reading from/writing to excel files within while loops, instead of holding them in the memory - if it is not essential.