PREG_CLASS_CJK
in modules/search/search.module
Matches all CJK characters that are candidates for auto-splitting (Chinese, Japanese, Korean). Contains kana and BMP ideographs.
<?php
define('PREG_CLASS_CJK', '\x{3041}-\x{30ff}\x{31f0}-\x{31ff}\x{3400}-\x{4db5}'.
'\x{4e00}-\x{9fbb}\x{f900}-\x{fad9}');
?>