exception handling in plpgsql

hello

I am using the following sytex to handle exceptions in
plpgsql (I am using postgres 8 rc1)

....some code ........

EXCEPTION   WHEN NO_DATA THEN            RAISE NOTICE 'NO DATA';   WHEN OTHERS THEN       RAISE NOTICE 'An exception
occurred';      RETURN emp_rec;
 

and i receive the following error 
ERROR:  unrecognized exception condition "no_data"

How can i rectify this error?

    
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