use Socket qw( inet_aton inet_ntoa );

while (<DATA>) {
   my ($swit,$server,$ip_range) = split;
   $server = "${swit}_$server";

   my ($start, $end) = split /-/, $ip_range;
   my $start_n = unpack('N', inet_aton($start));
   my $end_n   = unpack('N', inet_aton($end));
   for my $ip_n ($start_n..$end_n) {
      push @{ $servers{$server} }, inet_ntoa(pack('N', $ip_n));
   }
}