sub isHostValid{
        my $host = shift;
	my $NSLOOKUP = '/usr/bin/nslookup';
	
  	$/='';
	my $fh = new IO::File "$NSLOOKUP -type=any $host 2>&1 |";
	my @response = <$fh>;
      	close $fh;
      	$/='\n';
      	
      	if (grep /Name:\s+$host/, @response){
      		return 1;   
      	}
      	
      	return 0;
}