C:\Users\xyz\Desktop>chak.pl
     
 Letters At 1st & 2nd Positions:
  AT=4;  Letters At 1st & 2nd Positions:
  TC=0;  Letters At 1st & 2nd Positions:
  AC=0;

 Letters At 2nd & 3rd Positions:
  AT=0;  Letters At 2nd & 3rd Positions:
  TC=4;  Letters At 2nd & 3rd Positions:
  AC=0;

 Letters At 1st & 3rd Positions:
  AT=0;  Letters At 1st & 3rd Positions:
  TC=0;  Letters At 1st & 3rd Positions:
  AC=0;(It is wrong; should be AC=4)