/* Take a copy since we're about to overwrite TARG */
olds = s = (U8*)savepvn((char*)s, len);
}
- if (!SvOK(left) && SvTYPE(left) <= SVt_PVMG)
- sv_setpv(left, ""); /* Suppress warning. */
+ if (!SvOK(left) && SvTYPE(left) <= SVt_PVMG) {
+ if (SvREADONLY(left))
+ left = sv_2mortal(newSVsv(left));
+ else
+ sv_setpv(left, ""); /* Suppress warning. */
+ }
l = (U8*)SvPV(left, targlen);
left_utf |= DO_UTF8(left);
if (TARG != left)