SCM prev = ly_module_lookup (mod, sym);
if (scm_is_true (prev))
val = nested_property_alist (scm_variable_ref (prev), path, val);
SCM prev = ly_module_lookup (mod, sym);
if (scm_is_true (prev))
val = nested_property_alist (scm_variable_ref (prev), path, val);