Compare two strings/dates/numbers in SQL -> MERGE$ACTIONS

Below queries replace characters or numbers or date  as a ‘B', for any characters that differ between the two strings.

SQL> select MERGE$ACTIONS('ABC', 'ABD') FROM DUAL;

MER
---
ABB

SQL> select MERGE$ACTIONS('ABC', 'ABCD') FROM DUAL;
MER
---
ABC

SQL> select MERGE$ACTIONS('ABC', 'ABC') FROM DUAL;
MER
---
ABC

SQL> select MERGE$ACTIONS(1234,1294) FROM DUAL;
MERG
----
12B4

SQL> select sysdate,MERGE$ACTIONS(sysdate, sysdate-1) from dual;
SYSDATE   MERGE$ACTIONS(SYSD
--------- ------------------
23-JAN-13 2B-JAN-13