my $id = $self->query->param('id');
 $self->param("object") = $self->get_obj($id) if $id;

##</code><code>##

sub foo {
   my $self = shift;
   my $object = $self->param("object") or return $self->get_id();
   # ... the rest 

}

##</code><code>##

sub cgiapp_prerun {
  # ...
  my $id = $self->query->param('id');
  if (!$id) {
     return $self->prerun_mode('get_id');
  }
  $self->param("object") = $self->get_obj($id);
# ...
}