a=: 'pqr' [ b=: 'PQR'
   m=: 3 3$ 'abcdefghi' [ n=: 3 3$ 'ABCDEFGHI'
  
   a (; ; , ; ,. ; ,:) b
+---------+------+--+---+
|+---+---+|pqrPQR|pP|pqr|
||pqr|PQR||      |qQ|PQR|
|+---+---+|      |rR|   |
+---------+------+--+---+
  
   m (; ; , ; ,. ; ,:) n
+---------+---+------+---+
|+---+---+|abc|abcABC|abc|
||abc|ABC||def|defDEF|def|
||def|DEF||ghi|ghiGHI|ghi|
||ghi|GHI||ABC|      |   |
|+---+---+|DEF|      |ABC|
|         |GHI|      |DEF|
|         |   |      |GHI|
+---------+---+------+---+

   a (; ; , ; ,. ; ,:) n
+---------+---+----+---+
|+---+---+|pqr|pABC|pqr|
||pqr|ABC||ABC|qDEF|   |
||   |DEF||DEF|rGHI|   |
||   |GHI||GHI|    |   |
|+---+---+|   |    |ABC|
|         |   |    |DEF|
|         |   |    |GHI|
+---------+---+----+---+
  
   m (; ; , ; ,. ; ,:) b
+---------+---+----+---+
|+---+---+|abc|abcP|abc|
||abc|PQR||def|defQ|def|
||def|   ||ghi|ghiR|ghi|
||ghi|   ||PQR|    |   |
|+---+---+|   |    |PQR|
|         |   |    |   |
|         |   |    |   |
+---------+---+----+---+