Guess I didn't step away enough to have it make sense to anyone else....

That said, here's some code:

sub cgiapp_prerun {

   my $self = shift;

   my $dbh     = $self->{DBH} = $self->param('DBH');

   ### let's check for storage;

   my $previousClass = $self->query->param('this');

   my $className = "DataClasses::${previousClass}";

   if ( $className->SUPER::can( 'new' ) 
          and $className->SUPER::can( 'store') ) {
      my $object = $className->new( 
           DBH => $dbh, REQUEST => $request );

      ## the needStorage method allows us to 
      ## have multiple "screens" using the same class 
      ## where not all of them store in the DB

      $object->store() if $object->needStorage();
      }
   }

}
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and the store() method ...

sub store {

    my ( $self, %params )_ = @_;

    ### if insert ... 

    $self->query->param( -name => 'whatever', -value => '123');
    $self->param( 'whatever', '123' );

    return 1;
}
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both methods of stashing the value until the runmode is executed failed. as i've understood the calling stack:

CGI::App->new() -> prerun -> setup -> "runmode" -> teardown

so i don't see how something set in one mode wouldn't carry into another, because it's the same "run cycle".