set something 111.111.111.111 255.255.255.0

##</code><code>##

if (/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/){
  s/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/xxx.xxx.xxx.xxx/;
  print VPNOUTFILE "$_";
}

##</code><code>##

set something xxx.xxx.xxx.xxx 255.255.255.0

##</code><code>##

set something xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx