function wp_targeted_link_rel_callback( $matches ) {
	$link_html = $matches[1];
	$rel_match = array();

	/**
	 * Filters the rel values that are added to links with `target` attribute.
	 *
	 * @since 5.1.0
	 *
	 * @param string $rel       The rel values.
	 * @param string $link_html The matched content of the link tag including all HTML attributes.
	 */
	$rel = apply_filters( 'wp_targeted_link_rel', 'noopener noreferrer', $link_html );

	// Avoid additional regex if the filter removes rel values.
	if ( ! $rel ) {
		return "<a $link_html>";
	}

	// Value with delimiters, spaces around are optional.
	$attr_regex = '|rel\s*=\s*?(\\\\{0,1}["\'])(.*?)\\1|i';
	preg_match( $attr_regex, $link_html, $rel_match );

	if ( empty( $rel_match[0] ) ) {
		// No delimiters, try with a single value and spaces, because `rel =  va"lue` is totally fine...
		$attr_regex = '|rel\s*=(\s*)([^\s]*)|i';
		preg_match( $attr_regex, $link_html, $rel_match );
	}

	if ( ! empty( $rel_match[0] ) ) {
		$parts     = preg_split( '|\s+|', strtolower( $rel_match[2] ) );
		$parts     = array_map( 'esc_attr', $parts );
		$needed    = explode( ' ', $rel );
		$parts     = array_unique( array_merge( $parts, $needed ) );
		$delimiter = trim( $rel_match[1] ) ? $rel_match[1] : '"';
		$rel       = 'rel=' . $delimiter . trim( implode( ' ', $parts ) ) . $delimiter;
		$link_html = str_replace( $rel_match[0], $rel, $link_html );
	} elseif ( preg_match( '|target\s*=\s*?\\\\"|', $link_html ) ) {
		$link_html .= " rel=\\\"$rel\\\"";
	} elseif ( preg_match( '#(target|href)\s*=\s*?\'#', $link_html ) ) {
		$link_html .= " rel='$rel'";
	} else {
		$link_html .= " rel=\"$rel\"";
	}

	return "<a $link_html>";
}