npfvar_expand_string
vp = npfctl_parse_ifnet(npfvar_expand_string(vp),
char *s = npfvar_expand_string(npfvar_lookup($4));
char *s = npfvar_expand_string(npfvar_lookup($1));
$$ = npfvar_expand_string(vp);
rid_type = npfvar_expand_string(vp);
char * npfvar_expand_string(const npfvar_t *);