Oh man, super rookie mistake there- thanks for catching that. However, even when corrected, it prints:
A from FILE1 with number 1_1 and A from FILE2 with number 2_1 match
A from FILE1 with number 1_2 and B from FILE2 with number 2_2 DO NOT match
B from FILE1 with number 1_3 and from FILE2 with number DO NOT match
C from FILE1 with number 1_4 and from FILE2 with number DO NOT match

and is still is missing two of the matches and two of the mismatches, so that's in the looping.