There is a friendly url subsystem used by the CMS, really all CMS pages are served by /Default.aspx?pageid=x and friendly urls are mapped to the appropriate real url by our url re-writer.
I'm not sure about any easy way to hook in your parsing logic, but you could manually create friendly urls in Administration > Advanced Tools > Url Manager
You could create a friendly url country_GB.aspx and map it to a real url /country.aspx?code=GB
and so on for other countries.
A more complex solution that would allow parsing logic would be to implement a custom httphandler and then map it to handle all requests like country*.ashx from the Web.config handlers section, then in your handler you can do whatever parsing and redirect logic you like. Also you ca implement this handler a custom class library project so it lives in its own dll separate from mojoportal code.
Hope it helps,