#!/usr/bin/env perl

use strict;
use warnings;

use XML::Simple;

my $in_file = "in.xml";
my $xml_file = 'out.xml';

my $xml = XMLin(
    $in_file,
    KeepRoot => 1,
    ForceArray => 1,
);

# show me what the data look like
use Data::Dumper;
warn Dumper $xml;


### Save a Reference to the first "attribut" tag
my $ref = $xml->{importrecord}->[0]
  ->{aktionen}->[0]
  ->{transaktion}->[0]
  ->{aktion}->[0]
  ->{parameter}->[0]
  ->{attribut}->[0];

# add new additional attribute into the referenced tag
$ref->{foo} = 'bar';

# add content via ->{content}, so now attributes are preserved and stay
$ref->{content} = 'Anlegen';


XMLout(
    $xml,
    KeepRoot => 1,
    NoAttr => 0,
    OutputFile => $xml_file,
);