$ paste file1 file2 | perl -lane 'print "@F[1,0,2,3]"'
	1 a 6 11
	2 b 7 12
	3 c 7 13
	4 d 8 14
	5 e 9 23

##</code><code>##

    $ paste file1 file2 | awk '{print $2, $1, $3, $4}'