sub fix_umlaut {
	my ( $tagname, $attr, $text ) = @_;
	$output .= $text;
	if ( $tagname eq 'idx:orth' && $attr->{value} =~ s/([$um])/$replace{$1}/g ) {
		$output .= qq{<idx:orth value="$attr->{value}"/>};  # repeat the tag with modified umlauts
	}
}