while (<REIN>) {
    chomp();
    my @we = split(/\t/);
    my $out_file_name = "out_file_nr_$we[0]";
    open my $RAUS, ">", $out_file_name or die "could not open $out_file_name $!";
    my $fix = "$we[0]\t$we[1]\t$we[2]\t$we[3]";
    my $out1 = "$we[4]\t$we[5]\t$we[6]\t$we[7]\t$we[8]\t$we[9]\t$we[10]\t$we[11]\t$we[12]";
    print $RAUS $fix ."\t" .$out1."\n"; 
    close $RAUS;
} 
close(REIN)

##</code><code>##

while (<$REIN>) {
    my $out_file_name = "out_file_nr_[$.]"; # $. is the line number on the last read file handle
    open my $RAUS, ">", $out_file_name or die "could not open $out_file_name $!";
    print $RAUS $_; 
    close $RAUS;
} 
close(REIN)