"I do not have much time now - I will try to learn the perl-xml stuff in the near future I hope" is exactly backwards. If you haven't much time now to solve the problem then far and away the best option is to ask for help using something like XML::Twig or possibly XML::TreeBuilder (not XML::Simple btw - it isn't).

For example, consider the following code using XML::TreeBuilder:

use strict;
use warnings;
use XML::TreeBuilder;

my $xmlDoc = <<XML;
<doc>
...
</doc>
XML

my $root = XML::TreeBuilder->new ();

$root->parse ($xmlDoc);

my @authors = $root->look_down (_tag => 'Author');

for my $authorElt (@authors) {
    my ($lastName) = $authorElt->look_down (_tag => 'LastName');
    my ($foreName) = $authorElt->look_down (_tag => 'ForeName');

    next unless defined $lastName and defined $foreName;

    print $lastName->as_text (), ', ', $foreName->as_text (), "\n";
}
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with the ... replaced by your sample XML prints (assuming the spurious </Article> is removed):

van Beilen, J B
Penninga, D
Witholt, B
Wilde, A
Reaves, B
Banting, G
[download]