sort {$a cmp $b}

##</code><code>##

struct in_addr {
    union {
        struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
        struct { u_short s_w1,s_w2; } S_un_w;
        u_long S_addr;
    } S_un;
}

##</code><code>##

use strict;
use Socket qw( inet_aton inet_ntoa);

local $, = $/;
print map  { inet_ntoa($_) }
      sort { $a cmp $b }
      map  { chomp; inet_aton($_) }
      <DATA>;
    print $/;
__DATA__
128.1.1.0
127
23.4.5.6
255.255.255.255
45.27.128.0
localhost