This code looks pretty good, at least at a first glance. You use heredocs in some places, but not in others. It would be good to use them everywhere.

The biggest thing that jumps out is that you are not testing whether open succeeds or fails. Also, the data files appear to be in the same directory as the CGI script. This is definitely not a clever idea. Put them under your home directory, or something, but get them out from under the web document tree.

Finally, if you want to try this out on a webserver, if you ask jcwren nicely he'll give you an account on perlmonk.org.

g r i n d e r