use strict;
use warnings;

my %config = map { /(.*)=(.*)/ } <DATA>;
$config{'IPADDR'} = '1.2.3.4';
print "$_=$config{$_}\n" for keys %config;

__DATA__
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
TYPE=Ethernet
IPADDR=10.9.0.200
NETMASK=255.255.0.0
GATEWAY=10.9.1.254