Looks like you're going to want to investigate:

Getting CGI parameters (look at the CGI.pm module);

file permissions, locking, etc.;

sending mail (possibly, if you want to send the form through mail) (look at Mail::Mailer, Mail::Sendmail, Net::SMTP).

Look at the CGI reference section on perl.com. You may also want to look at The Idiot's Guide to Solving Perl CGI Problems.

You need to decide how you want to store the form on the server. In a file? In a database? If the latter, take a look at DBI.