#!/usr/bin/env perl
use strict;
use warnings;

$/ = "{S:{CON:}}";

while (<DATA>)

{
if ( /\{108\:(\w+)\}\}/ ) {
                print "$1\n";
   }
}

__DATA__
{1:6392495900}{4:{177:1807300738}{451:1}{405:K22005}{108:8480963411}}{1:6392495900}{2:IVSN}{3:{108:8480963411}}{5:{MAC:00000000}{CHK:9F11}}{S:{CON:}}${1:6392495903}{4:{177:1807300738}{451:1}{405:K22005}{108:8481963413}}{1:6392495903}{2:IVSN}{3:{108:8481963413}}{5:{MAC:00000000}{CHK:12846}}{S:{CON:}}