sub sqlSingleRow( $sql, @placeholders ) {
    my $sth = $dbh->prepare( $sql );
    $sth->execute(@placeholders);

    # Do you really get only ever a single row back?
    my  (@r)=$c->fetchrow();
    $c->finish();
    return @r;
}

##</code><code>##

    my $sql_cat = <<'SQL';
        select ref_categorie
          from categorie_libelle_langue
             , libelle
             , langue
          from ref_categorie
         where libelle.libelle = ?
           AND categorie_libelle_langue.ref_libelle = libelle.id_libelle
           AND categorie_libelle_langue.ref_langue = langue.id_langue AND langue.key = ?
SQL

    my ($cat) = sqlSingleRow($sql_cat, $category, $lang );