package LookupFactory;

use base qw( UserSource );

sub init_lookup {
  # run config based upon type of source requested
}

package UserSource;

sub get {
  # get the type of user source (lookup, database, whatever)
}

package User

sub new {
  # get a source based upon whatever the User config says to get
}

package App

$user = User->new();

$user->info() # look ma!  no config!