package MyDB;
use base 'Class::DBI';

__PACKAGE__->set_db('Main', 'dbi:mysql:mydb', &db_login_credentials);

sub db_login_credentials {
  my $group = &who_is_this;
  if ($group eq 'staff') {
    return ('staff', 'password');
  } elsif ($group eq 'public') {
    return ('public', 'password');
  } else {
    die 'who is this person?';
  }
}

sub who_is_this {
  # do whatever it takles to figure out if it's public or 
  # staff, and return either 'staff' or 'public';
}


if (&who_is_this eq 'public') {
  __PACKAGE__->add_trigger(before_create => 
                           sub { die 'not authorized to create'; });
  __PACKAGE__->add_trigger(before_update => 
                           sub { die 'not authorized to update'; });
  __PACKAGE__->add_trigger(before_delete => 
                           sub { die 'not authorized to delete'; });
}