let site_mod = module{
    hostname="",
    port=0,
    db="localhost",
    db_user="admin",
    db_pass="password"
} => { // mods do not close over their environment.
    
    // this binding is not visible outside of the module. should be at the time of definition?
    // or path should be rewritten to be absolue before instantiation.
    let shared = import "../../shared.ucg";

    // processing should be delayed till module instantiation.
    let base_config = shared.mk_site_config(mod.hostname, mod.port); 

    let config = base_config{ // processing should also be delayed.
        dbs = [
            {
                database = mod.db,
                user = mod.db_user,
                pass = mod.db_pass,
            },
        ],
    };
};