Molecules made of molecules?
The key to your question lies in the word "bound". Without mentioning the state of your species we can say in general, species which are joined by covalent bonds are single molecules, there are countless examples of such reactions in organic chemistry where two small molecules condense into a single molecule. 

Species with intramolecular forces (hydrogen bonds, van der waals etc) can be called bound or perhaps "clusters", which is quite a broad term. Real bonding however is not so easily defined as the molecular orbitals may  generate a wide spectrum of charge distributions etc. Quantum mechanics gives a much clearer description of the bonding of a particular molecule or extended system. 

The terminology you write your $\ce{H2OHCl}$ is similar to how we write water of crystallisation in a solid. If this is where your idea came from, it should be remarked that this is a distinct concept. 

To conclude; species that are covalently bound (that could have strong polarisation even to bordering ionic bonding) are molecules. Intermolecular forces are precisely that, between distinct molecules. We should remark that we can also have extended solids with covalent bonding (e.g. group 14). In addition some regard metals as molecules too, molecules whose molecular orbitals are distributed over the entire structure etc (research tight binding model for more information). But I feel that wasn't the focus of your question?