SQL & PL/SQL

Hello All,

I have created below function which return BOOLEAN value :

CREATE OR REPLACE FUNCTION FUNC_1
(
P_EMPID IN emp.empno%type
)RETURN BOOLEAN
AS
L_VAR NUMBER;
BEGIN
SELECT 1 INTO L_VAR
FROM EMP
WHERE EMPNO = P_EMPID;

IF L_VAR = 1 THEN
RETURN TRUE;
ELSE
RETURN FALSE;
END IF;
END;

Now I want to call this function from SELECT but I know that SQL does not support BOOLEAN value so I tried in other way i.e. via CASE

SELECT CASE FUNC_1(7788)
       WHEN TRUE THEN 'TRUE'
       WHEN FALSE THEN 'FALSE'
       ELSE 'NULL'
       END CASE
FROM DUAL

But it is giving me error "ORA-00904: "FALSE": invalid identifier'

How can I achieve this ?

Thanks & Regards,
Rakesh