# This looks wrong, but it's what you gave us
my $batches = $data->{Jobs}{Job}{Blocks}{Block}{Batches}{Batch};

for my $batch (@$batches) {
    # This looks also wrong
    my $item = $batch->{Items}{Item};
    print $item->{CorporateName} . "\n";
    print $item->{Amount} . "\n";
}
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my $jobs =$data->{Jobs}{Job};
for my $job (@$jobs) {
    my $blocks = $job->{Blocks}{Block};
    for my $block (@$blocks) {
        my $batches = $job->{Batches}{Batch};
        for my $batch (@$batches) {
            my $items = $batch->{Items}{Item};
            for my $item (@$items) {
                print $item->{CorporateName} . "\n";
                print $item->{Amount} . "\n";
            }
        }
    }
}
[download]

By the way , the following would simplify your tree:

GroupTags => {
    Jobs    => 'Job',
    Blocks  => 'Block',
    Batches => 'Batch',
},
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