PERLVAR(self, perl_os_thread) /* Underlying thread object */
PERLVAR(flags, U32)
PERLVAR(threadsv, AV *) /* Per-thread SVs ($_, $@ etc.) */
+PERLVAR(threadsvp, SV **) /* AvARRAY(threadsv) */
PERLVAR(specific, AV *) /* Thread-specific user data */
PERLVAR(errsv, SV *) /* Backing SV for $@ */
PERLVAR(errhv, HV *) /* HV for what was %@ in pp_ctl.c */