This solution is actually on the right track.

The only mistake is that the author thought the result from inet_aton is a number, but it is not. In fact, the result returned is a string.

Simply modify that sort statement to:

sort {$a cmp $b}
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Now this piece of code works properly (I tested the modified version).

If you are interested in details, inet_aton converts ascii address into a c structure in_addr, i.e.

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;
}
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,which Perl interprets as a string, not an unsigned long.

My testing 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
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