help with sh script

[fbsd_user]

std_text='No ALTQ support in kernel ALTQ related functions disabled'
ret_ob='No ALTQ support in kernel ALTQ related functions disabled
OK'

ret_ob=`printf "$ret_ob" | sed 's/\$std_text//g'`
Does not strip off the std_text stuff.

How would I code a statement to remove everything from $ret_ob
but the ok at the end so $ret_ob would only contain the ok??

Some times $ret_ob will end in some error message and that is
what I want to capture after striping off the std_text.


Thanks