Code:
SQL> select * from xyz;

X
--------------------
elmer fudd

SQL> select * from abc;

Y
--------------------
fudd, elmer

SQL> edit
Wrote file afiedt.buf

  1   select xyz.x, abc.y
  2   from xyz, abc
  3   where trim(xyz.x) =
  4     trim(substr(y, instr(y,',')+1,
  5        length(y)) || ' ' ||
  6*       substr(y,1, instr(y,',')-1))
SQL> /

X                    Y
-------------------- --------------------
elmer fudd           fudd, elmer
Can you say "full table scan baby"? Also, this method has tons of potential for error... As pando says, make your data clean.