SQL> SET VERIFY OFF
SQL> DECLARE
  2      l_delim         VARCHAR2(1)   := ',';
  3      l_string        VARCHAR2(100) := 'SCWID,CWT,COT,ACB,AR';
  4      l_candidate     VARCHAR2(20)  := '&candidate';
  5      l_keyword       VARCHAR2(4);
  6  BEGIN
  7      IF (INSTR(l_delim || l_string || l_delim
  8          ,     l_delim || l_candidate || l_delim) = 0) THEN
  9          l_keyword := 'not ';
 10      END IF;
 11      DBMS_OUTPUT.PUT_LINE('"'
 12                           || l_candidate
 13                           || '" is '
 14                           || l_keyword
 15                           || 'in "'
 16                           || l_string
 17                   || '".');
 18  END;
 19  /
Enter value for candidate: COT
"COT" is in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: JUNK
"JUNK" is not in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: AR
"AR" is in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: CWID
"CWID" is not in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: SCWID
"SCWID" is in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: W
"W" is not in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: ABC
"ABC" is not in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL> /
Enter value for candidate: ACB
"ACB" is in "SCWID,CWT,COT,ACB,AR".
  
PL/SQL procedure successfully completed.
  
SQL>