PAIRED: lab1_set1.txt and lab1_set2.txt
BAD FILENAME: oops___should_not_be_in_this_list.txt
PAIRED: lab2_set1.txt and lab2_set2.txt
NOT PAIRED: lab3_set2.txt
NOT PAIRED: lab4_set1.txt
PAIRED: lab99_set1.txt and lab99_set2.txt
BAD FILENAME: lab100_set1.txts
NOT PAIRED: lab100_set2.txt
NOT PAIRED: lab101_set1.txt
BAD FILENAME: lab101_set2.txts