OP_NULL_CHECK_START  379 regcomp.c          r = add_opcode(reg, OP_NULL_CHECK_START);
OP_NULL_CHECK_START 6227 regcomp.c        { OP_NULL_CHECK_START,    "null-check-start",     ARG_MEMNUM  },
OP_NULL_CHECK_START 2713 regexec.c          CASE(OP_NULL_CHECK_START)  MOP_IN(OP_NULL_CHECK_START);