Let me rephrase my question:

You don't rephrase, you just repeat the contents of your OP... ;)

I am unsure How I can do what you and dragonchild suggest.

Did you even try? You provided me with a hash; I showed you the correct structure which would produce the output you described as desired. You have to transform your original hash, either in-place or by stuffing members into another temporary structure. What pieces of the hash transformation are difficult for you?

Okay, here' a complete working example. Since you provide sample data which is a bit inconsistent compared to the expected output (there's no structure member for the "No" attribute, so I just deduce them from the sorted hash keys) you will have to adapt the following for your real data, I guess.

use XML::Simple;

# your structure
$FIELDS = {
    'AA' => {
        'Description' => '',
        'Type' => 'Module',
        'File' => 'Sample1.pl',
    },
    'BB' => {
        'Description' => 'Initiator',
        'Type' => 'Methods',
        'File' => 'Sample1.pl',
    },
    'CC' => {
        'Description' => 'Destructor',
        'Type' => 'Methods',
        'File' => 'Sample2.pl',
        'Values' => {
            '1' => 'Ignore',
            '2' => 'Retry',
            '3' => 'Abort',
        }
    }
};

# hash transformation, in-place
my $c;
for my $key (sort keys %$FIELDS) {

    $FIELDS->{$key}->{Label} = $key;
    $FIELDS->{$key}->{No}    = ++$c;

    for my $label (qw(Description Type File)) {
        $FIELDS->{$key}->{$label} = { content => $FIELDS->{$key}->{$la
+bel} };
    }

    if (exists $FIELDS->{$key}->{Values}) {

        my $values_hash = $FIELDS->{$key}->{Values};

        $FIELDS->{$key}->{Values} = [
            map {
                { No => $_, content => $values_hash->{$_} }
            } sort keys %$values_hash
        ];
    }
}

# output the XML
print XMLout(
    {
        data => {
            Node => [
                map $FIELDS->{$_}, sort keys %$FIELDS
            ]
        }
    }
);
__END__
<opt>
  <data>
    <Node Label="AA" No="1">
      <Description></Description>
      <File>Sample1.pl</File>
      <Type>Module</Type>
    </Node>
    <Node Label="BB" No="2">
      <Description>Initiator</Description>
      <File>Sample1.pl</File>
      <Type>Methods</Type>
    </Node>
    <Node Label="CC" No="3">
      <Description>Destructor</Description>
      <File>Sample2.pl</File>
      <Type>Methods</Type>
      <Values No="1">Ignore</Values>
      <Values No="2">Retry</Values>
      <Values No="3">Abort</Values>
    </Node>
  </data>
</opt>
[download]

Hope that helps. I won't repeat the example for XML::Writer or XML::Twig; their requirements for input data might be different. But AFAIK there's no module which produces valid XML from your hash as is.

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                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}