[Serusers] Search trough status line for specific reason phrase

Dear, is there any way to search inside Status-Line of response message? I have strange b2bua that always returns SIP 500 just with different reason phrase. I need to match on them so that I can rewrite failure messages. I thought about something like this: failure_route[1] { if (t_check_status("500")) { #here I need to search trough status line for specific reasons, but have no idea how to do that if (search("^Specific message")) { t_reply("480", "Temporarily Unavailable"); break; } } } Thank you J.