$c->stash->{logo} = ($c->config->{hydra_logo} // $ENV{"HYDRA_LOGO"}) ? "/logo" : "";

    $c->stash->{logo} = defined $c->config->{hydra_logo} ? "/logo" : "";

    my $path = $c->config->{hydra_logo} // $ENV{"HYDRA_LOGO"} // die("Logo not set!");

    my $path = $c->config->{hydra_logo} // die("Logo not set!");