## sv.c
PP(pp_vec)
{
    dVAR; dSP; dTARGET;
    register const IV size   = POPi;
//    register const IV offset = POPi;
    register const UV offset = POPi;
    register SV * const src = POPs;


## doop.c
UV
//Perl_do_vecget(pTHX_ SV *sv, I32 offset, I32 size)
Perl_do_vecget(pTHX_ SV *sv, U32 offset, I32 size)
...

void
Perl_do_vecset(pTHX_ SV *sv)
{
    dVAR;
//    register I32 offset, bitoffs = 0;
    register U32 offset
    register I32 bitoffs = 0;
    register I32 size;
    register unsigned char *s;
    register UV lval;
    I32 mask;
    STRLEN targlen;
    STRLEN len;
    SV * const targ = LvTARG(sv);

    if (!targ)
	return;
    s = (unsigned char*)SvPV_force(targ, targlen);
    if (SvUTF8(targ)) {
	/* This is handled by the SvPOK_only below...
	if (!Perl_sv_utf8_downgrade(aTHX_ targ, TRUE))
	    SvUTF8_off(targ);
	 */
	(void) Perl_sv_utf8_downgrade(aTHX_ targ, TRUE);
    }

    (void)SvPOK_only(targ);
    lval = SvUV(sv);
    offset = LvTARGOFF(sv);
//    if (offset < 0)
//	Perl_croak(aTHX_ "Negative offset to vec in lvalue context");