void unset_property (SCM var_sym);
void instrumented_set_property (SCM, SCM, const char *, int, const char *);
void internal_set_property (SCM var_sym, SCM value);
void unset_property (SCM var_sym);
void instrumented_set_property (SCM, SCM, const char *, int, const char *);
void internal_set_property (SCM var_sym, SCM value);