monks: gather your stones while I don my armor...

maybe perl isn't the best tool here

$ cat abc
a
b
c
d
e
e
e
ff
fff
g
$ cat abc2
a
fff
e
g
e
e
b
c
d
ff
$ sort abc > sorted_abc
$ sort abc2 > sorted_abc2
$ diff -u sorted_abc sorted_abc2
$ rm sorted*
[download]

Then edit one of the files and repeat. You'll get a diff. In the above case no diff is shown because the files are the same when sorted.