setup the "select" and "update" users on mysql with according permissions.
the cgi for the selects uses the "select" created mysql user and the updating cgi uses the "update" user during DBI->Connect.
It's wiser to have separate mysql logins like this as the select cgi would likely collect data from a form and you may end up with injected code to escalate their mysql priviledges. Then you can just concentrate on making the update cgi nice and tight in terms of security.