XML::Simple seems to ignore comments.

use warnings;
use strict;
use XML::Simple;
use Data::Dumper;

my $xml = '
<foo>
    <bar>123</bar>
    <!-- COMMENT -->
    <bar>abc</bar>
</foo>
';

my $ref = XMLin($xml);
print Dumper($ref);

__END__

$VAR1 = {
          'bar' => [
                   '123',
                   'abc'
                 ]
        };
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Please show a small snippet of your XML file and the contents of your $xmlFileKeyAttr (both with comments).