OP_PUSH_STOP_BT  1388 regcomp.c            r = add_opcode(reg, OP_PUSH_STOP_BT);
OP_PUSH_STOP_BT  6235 regcomp.c        { OP_PUSH_STOP_BT,         "push-stop-bt",         ARG_NON },
OP_PUSH_STOP_BT  2996 regexec.c          CASE(OP_PUSH_STOP_BT)  MOP_IN(OP_PUSH_STOP_BT);