Replacing pre-defined variables and expressions by their value is applied only to keys that carry numerical data. For example: atoms, define, units. However, it is not applied to keys that carry electronic occupation numbers.
Note that when parsing applies to a given key the whole record of the key (key + argument) and its data block are parsed. The parsing then applies to all items, even those that in themselves have no numerical meaning (for instance, the atom type names in the atoms data block are scanned and must of course then not be 'defined' as identifiers with a numerical value.
