input files
file0	file1	
1	     2	
2	     4
3	     5
5	     8
7	     9
9

logical test
1<=>2	-1	next 0, keep 1, print to nomatch0
2<=>2	 0	next 0, next 1, print to match
3<=>4	-1	next 0, keep 1, print to nomatch0
5<=>4	 1	keep 0, next 1, print to nomatch1
5<=>5	 0	next 0, next 1, print to match
7<=>8	-1	next 0, keep 1, print to nomatch0
9<=>8	 1	keep 0, next 1, print to nomatch1
9<=>9	 0	next 0, next 1, print to match

output files
matched	nomatch0   nomatch1
2	      1	       4
5	      3	       8
9	      7