#!/usr/bin/perl

use warnings;
use strict;

while(my $zeile = <DATA>) {

   my @array =  ();
   @array    = split(/\./, $zeile);

   print join("\n", $array[0])."\n";

} # while
__DATA__
Auto.VW.Golf.BJ
Auto2.VW.Polo.BJ
Auto3.Audi.A5.BJ
Auto4.Audi.A4.BJ
Auto5.Audi.A3.BJ