Found a bug in form validation with regex_match

[eluser]Unknown[/eluser]
I found a bug when I try to use regex_match like this:

'rules' => 'required|regex_match[[A|B]]'

if I use only [AB] instead of [A|B], regex_match function works properly,

but when I try to use [A|B], the CI_Form_validation class works wrong.

I found it caused by the seperator '|'.

How can I report this bug?