T_REFANDSV
    ".(unshift(@line, (
    'PREINIT:',
    '    SV * '.$var.'Ref;',
    'INPUT:')),'').
    "${\$var}Ref = $arg;
    if (SvROK(${\$var}Ref))
        $var = (SV*)SvRV(${\$var}Ref);
    else
        Perl_croak(aTHX_ \"%s: %s is not a reference\",
            ${$ALIAS?\q[GvNAME(CvGV(cv))]:\qq[\"$pname\"]},
            \"$var\");