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 */
PERLVAR(mutex, perl_mutex) /* For the fields others can change */
PERLVAR(tid, U32)
PERLVAR(prev, struct perl_thread *)