SET debug_dbug='+d,pcre_exec_error_123';
SELECT 'a' RLIKE 'a';
'a' RLIKE 'a'
0
Warnings:
Warning	1139	Got error 'pcre_exec: Internal error (-123)' from regexp
SET debug_dbug='';
SELECT 'a' RLIKE 'a';
'a' RLIKE 'a'
1