OP *
 Perl_ck_require(pTHX_ OP *o)
 {
     GV* gv;

     if (o->op_flags & OPf_KIDS) {       /* Shall we supply missing .pm? */
         SVOP *kid = (SVOP*)cUNOPo->op_first;

         if (kid->op_type == OP_CONST && (kid->op_private & OPpCONST_BARE)) {
             char *s;
             for (s = SvPVX(kid->op_sv); *s; s++) {
                 if (*s == ':' && s[1] == ':') {
                     *s = '/';
                     Move(s+2, s+1, strlen(s+2)+1, char);
                     --SvCUR(kid->op_sv);
                 }
             }
             if (SvREADONLY(kid->op_sv)) {
                 SvREADONLY_off(kid->op_sv);
                 sv_catpvn(kid->op_sv, ".pm", 3);
                 SvREADONLY_on(kid->op_sv);
             }
             else
                 sv_catpvn(kid->op_sv, ".pm", 3);
         }
     }

     /* handle override, if any */
     gv = gv_fetchpv("require", FALSE, SVt_PVCV);
     if (!(gv && GvCVu(gv) && GvIMPORTED_CV(gv)))
         gv = gv_fetchpv("CORE::GLOBAL::require", FALSE, SVt_PVCV);

     if (gv && GvCVu(gv) && GvIMPORTED_CV(gv)) {
         OP *kid = cUNOPo->op_first;
         cUNOPo->op_first = 0;
         op_free(o);
         return ck_subr(newUNOP(OP_ENTERSUB, OPf_STACKED,
                                append_elem(OP_LIST, kid,
                                            scalar(newUNOP(OP_RV2CV, 0,
                                                           newGVOP(OP_GV, 0,
                                                                   gv))))));
     }
 
     return ck_fun(o);
 }