This isn't quite sufficiently specified to write code for.

1) You talk about a bracketed "record" and nested within it bracketed "sub-records", but the main record and its single direct sub-record appear to have key-value pairs (like a hash structure), while the further nested sub-records appear to be simple lists (like an array structure). How is it intended to distinguish the one from the other? Is it just that the key "valid-values" introduces a list while anything else introduces a hash?

2) You talk about keys as "text" and values as "simple text" (if not a record), but there's an example of a quoted string ("The aws-ec2 parameters") and the unquoted string values include other punctuation marks. What characters can appear in unquoted text? What types of quoting can appear (double quotes, single quotes, other)? Can quote marks appear inside a quoted string, perhaps escaped somehow? Can quoted text include other whitespace, such as newlines?

3) The example shows four bits of text preceding the main record (sys ecm cloud-provider /Common/aws-ec2), what is supposed to happen with that text, is it to be ignored?

It would be useful to answer these questions, and confirm the answers by showing what data structure you would ideally like to see from this example (perhaps in the form of Data::Dumper output). Eg:

$VAR1 = {
  'description' => 'The aws-ec2 parameters',
  'property-template' => {
    'account' => {},
    'availability-zone' => {
      'valid-values' => [
        'a',
        'b',
        'c',
        'd'
      ]
    },
    'instance-type' => {
      'valid-values' => [
        't2.micro',
        't2.small',
        't2.medium'
      ]
    },
    'region' => {
      'valid-values' => [
        'us-east-1',
        'us-west-1'
      ]
    }
  }
};
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