in reply to User Who Modified File
On a *nix system, you can use stat to get the UID (user ID) of the file, and cross reference it with /etc/passwd to match it to the user.
For a windows system, I found this link: http://support.microsoft.com/kb/218965. It contains some sample VB code that you should be able to translate to perl. Though you'll have to define the DLL references & such.
Update: I also found a bit of perl at http://stackoverflow.com/questions/4677180/how-to-get-file-owner-name.
When your only tool is a hammer, all problems look like your thumb.