$re = '/(string@)([a-zA-ZÀ-ž]|\\\\[0-9]{3})+/u';
$str = 'string@řetězec\\032s\\032lomítkem\\032\\092\\032a\\010novým\\035řádkem
string@\\032<not-tag/>\\032';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php