...
    d = SvPVX(sv);
    while (isALPHA(*d)) d++;
    while (isDIGIT(*d)) d++;
    if (*d) {
#ifdef PERL_PRESERVE_IVUV
	/* Got to punt this as an integer if needs be, but we don't issue
	   warnings. Probably ought to make the sv_iv_please() that does
	   the conversion if possible, and silently.  */
	const int numtype = grok_number(SvPVX_const(sv), SvCUR(sv), NULL);
	if (numtype && !(numtype & IS_NUMBER_INFINITY)) {
	    /* Need to try really hard to see if it's an integer.
	       9.22337203685478e+18 is an integer.
	       but "9.22337203685478e+18" + 0 is UV=9223372036854779904
	       so $a="9.22337203685478e+18"; $a+0; $a++
	       needs to be the same as $a="9.22337203685478e+18"; $a++
	       or we go insane. */
	
	    (void) sv_2iv(sv);
	    if (SvIOK(sv))
		goto oops_its_int;

	    /* sv_2iv *should* have made this an NV */
	    if (flags & SVp_NOK) {
		(void)SvNOK_only(sv);
                SvNV_set(sv, SvNVX(sv) + 1.0);
		return;
	    }
	    /* I don't think we can get here. Maybe I should assert this
	       And if we do get here I suspect that sv_setnv will croak. NWC
	       Fall through. */
#if defined(USE_LONG_DOUBLE)
	    DEBUG_c(PerlIO_printf(Perl_debug_log,"sv_inc punt failed to convert '%s' to IOK or NOKp, UV=0x%"UVxf" NV=%"PERL_PRIgldbl"\n",
				  SvPVX_const(sv), SvIVX(sv), SvNVX(sv)));
#else
	    DEBUG_c(PerlIO_printf(Perl_debug_log,"sv_inc punt failed to convert '%s' to IOK or NOKp, UV=0x%"UVxf" NV=%"NVgf"\n",
				  SvPVX_const(sv), SvIVX(sv), SvNVX(sv)));
#endif
	}
#endif /* PERL_PRESERVE_IVUV */
	sv_setnv(sv,Atof(SvPVX_const(sv)) + 1.0);
	return;
    }
    d--;
    while (d >= SvPVX_const(sv)) {
	if (isDIGIT(*d)) {
	    if (++*d <= '9')
		return;
	    *(d--) = '0';
	}
	else {
#ifdef EBCDIC
	    /* MKS: The original code here died if letters weren't consecutive.
	     * at least it didn't have to worry about non-C locales.  The
	     * new code assumes that ('z'-'a')==('Z'-'A'), letters are
	     * arranged in order (although not consecutively) and that only
	     * [A-Za-z] are accepted by isALPHA in the C locale.
	     */
	    if (*d != 'z' && *d != 'Z') {
		do { ++*d; } while (!isALPHA(*d));
		return;
	    }
	    *(d--) -= 'z' - 'a';
#else
	    ++*d;
	    if (isALPHA(*d))
		return;
	    *(d--) -= 'z' - 'a' + 1;
#endif
	}
    }
    /* oh,oh, the number grew */
    SvGROW(sv, SvCUR(sv) + 2);
    SvCUR_set(sv, SvCUR(sv) + 1);
    for (d = SvPVX(sv) + SvCUR(sv); d > SvPVX_const(sv); d--)
	*d = d[-1];
    if (isDIGIT(d[1]))
	*d = '1';
    else
	*d = d[1];