char *
sv_append_till(sv,from,fromend,delim,keeplist)
register SV *sv;
register char *from;
register char *fromend;
register I32 delim;
char *keeplist;
{
    register char *to;
    register STRLEN len;

    if (SvREADONLY(sv))
	fatal(no_modify);
    if (!from)
	return Nullch;
    len = fromend - from;
    if (!SvUPGRADE(sv, SVt_PV))
	return 0;
    SvGROW(sv, SvCUR(sv) + len + 1);
    SvPOK_only(sv);		/* validate pointer */
    to = SvPV(sv)+SvCUR(sv);
    for (; from < fromend; from++,to++) {
	if (*from == '\\' && from+1 < fromend && delim != '\\') {
	    if (!keeplist)
		*to++ = *from++;
	    else if (from[1] && index(keeplist,from[1]))
		*to++ = *from++;
	    else
		from++;
	}
	else if (*from == delim)
	    break;
	*to = *from;
    }
    *to = '\0';
    SvCUR_set(sv, to - SvPV(sv));
    return from;
}