knoppix@Microknoppix:~$ cat xxxx
line 4
line 2
line 5
line 1
line 6
line 3
knoppix@Microknoppix:~$ cat xxxx | perl -E '
> say for sort map { chomp; $_ } <>;'
line 1
line 2
line 3
line 4
line 5
line 6
knoppix@Microknoppix:~$