OP_BACKREFN      1777 regcomp.c      	    r = add_opcode(reg, OP_BACKREFN);
OP_BACKREFN      6201 regcomp.c        { OP_BACKREFN,            "backrefn",             ARG_MEMNUM  },
OP_BACKREFN      2530 regexec.c          CASE(OP_BACKREFN)  MOP_IN(OP_BACKREFN);