It seems to me you have the biggest piece of the puzzle already. One way is to have a way of uniquely identifying each user; and to incorporate that unique identifier into the name of the file you save away. Since your users are authenticated before they ever get to see any content in the directory your CGI lives in, you *can* get the user's name at the time you generate the file in the first place, so this shouldn't be at all difficult.

If it's a function to get that name that you're looking for, CGI::remote_user()

My apologies if I'm missing something here.

Philosophy can be made out of anything. Or less -- Jerry A. Fodor