As far as non-functional PPMs go, I would suggest finding a dev machine with ActiveState Perl and a functioning PPM, then installing Statistics::Basic::StdDev and its dependencies. You can then copy the C:\Perl\site\lib\ file tree to your target machine. All the modules in question are pure Perl, so you shouldn't have any issues doing this.

Once you have that module in place, you'll be in a better position to determine the significance of differences between Excel and Perl's output.