OP_BACKREF1      1774 regcomp.c      	  case 1:  r = add_opcode(reg, OP_BACKREF1); break;
OP_BACKREF1      6199 regcomp.c        { OP_BACKREF1,            "backref1",             ARG_NON },
OP_BACKREF1      2520 regexec.c          CASE(OP_BACKREF1)  MOP_IN(OP_BACKREF1);