I was changed the description - hope it is clear now

There is one literal with symbol " ' " inside it. You can try this script:

declare
    a varchar2(100);
begin
    a:='data''s';
    dbms_output.put_line('a='||a);
end;

Output:
Start Script Execution ...
**** SCRIPT STARTED ****
declare
a varchar2(100);
...
PL/SQL block executed
a=data's
**** SCRIPT ENDED ****
End Script Execution