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

sub foo {
   my $self = shift;
...
   # ... the rest 

}

sub cgiapp_prerun {
  # ...
...
  $self->param("object") = $self->get_obj($id);
# ...
}