$fh = $query->upload('$filename');

##</code><code>##

$fh = $query->upload($filename);

##</code><code>##


eval {
    ## ...

    $fh = $query->upload($filename) 
            or die "No file uploaded: '@{[ $query->cgi_error() ]}'";

    ## ...
};
$@ and do {
     print_html($@);
};