declare

l varchar2(1);
m varchar2(1) := 'A';
bool boolean;

begin

  bool := (l=m);
  
  IF bool = TRUE THEN
  
    dbms_output.put_line('comparsion is true');
    
  ELSIF bool = FALSE THEN
  
    dbms_output.put_line('comparsion is false');
    
  ELSE
  
    dbms_output.put_line('comparsion is unknown');
    
  END IF;
  
  
  --With AND
  bool := (l=m) AND 1=1;
  
  IF bool = TRUE THEN
  
    dbms_output.put_line('AND comparsion is true');
    
  ELSIF bool = FALSE THEN
  
    dbms_output.put_line('AND comparsion is false');
    
  ELSE
  
    dbms_output.put_line('AND comparsion is unknown');
    
  END IF;
  
  IF NOT bool THEN
    dbms_output.put_line('NOT bool');
  ELSE
    dbms_output.put_line('NOT NOT bool, because it''s not false');
  END IF;
  
--  WITH OR
  bool := (l=m) OR 1=1;
  
  IF bool = TRUE THEN
  
    dbms_output.put_line('OR comparsion is true');
    
  ELSIF bool = FALSE THEN
  
    dbms_output.put_line('OR comparsion is false');
    
  ELSE
  
    dbms_output.put_line('OR comparsion is unknown');
    
  END IF;

  
end;

comparsion is unknown
AND comparsion is unknown
NOT NOT bool, because it's not false
OR comparsion is true

PL/SQL procedure successfully completed.