To take the right side of ::= as key is not so wise decision, because it is not unique.
My suggestion, create new data structure :

%hash_of_hash = ();
$key = 'S';
$new_data = {};
$new_data{'1'} = 'ASB';
$new_data{'2'} = '#$';
$new_data{'3'} = '$';

$hash_of_hash{$key} = $new_data;

# repeat for other data....
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