# Create a list of all possible IP addresses within subnet
open(ALLIP, ">allip.list") || die "Unable to create file: allip.list\n";
for ($i=0; $i<=20; $i++) {
        print ALLIP "$ip_subnet.$i\n";
        }
close(ALLIP);

open(ALLIP, "allip.list") || die "Unable to open file: allip.list\n";
open(PINGALLIP, ">pingallip.list") || die "Unable to open file: pingallip.list";
while (<ALLIP>) {
        chomp;
        system("ping $_ >>pingallip.list") && "Unable to create file: pingallip.
list";
        }
close(ALLIP);
close(PINGALLIP);

open(ALIVEIP, ">aliveip.list");
close(ALIVEIP);
open(ALIVEIP, "aliveip.list");
open(PINGALLIP, "pingallip.list") || die "Unable to open file: pingallip.list";
while (<PINGALLIP>) {
   if (/is alive/) {
                chomp;
                print ALIVEIP $_;
        }
}
close(PINGALLIP);