Amazing, thank you Garu !! You are very responsive indeed :-)

Here is what add() looks like now:

fun add ($c) {
    my ($data, $name) = @{$c->stash}{qw/data name/};

    $data->add($name);
}
[download]

Now that I'm more confident that App::Rad is what I need, I have printed the documentation (18 pages) and will read it all.
I had tried to use setup() instead of preprocess... because I hadn't read the whole doc.