Package SuperClass.pm
use DBI;
use whatever_else_you_want;
use base 'CGI::Application';

sub cgiapp_init{
   my $self=shift;
   ## initialize variables, stuff them into params to allow
   ## all other modules to inherit common functions. For
   ## instance, I'll set up my DBI connection, user
   ## authentication,  HTML::Template object, etc. all in 
   ## here. Then every object from here on down can access
   ## them.
   }