A bug on RAWTOHEX function

Hi, gurus,
I found a bug on RAWTOHEX function.
The return value are different when it is executed in PL/SQL and SQL. See the following example: (on Oracle8i, WinNT4 SP5)

SQL> declare
  2 a varchar2(8);
  3 begin
  4 a := rawtohex('AB');
  5 dbms_output.put_line(a);
  6 select rawtohex('AB') into a from dual;   7 dbms_output.put_line(a);
  8 end;
  9 /
AB
4142

PL/SQL procedure successfully completed. Received on Sat Nov 27 1999 - 09:15:38 CST