sub myvec(\$$$) :lvalue  {
    use constant TWO_GB => 2**31;
    my( $ref, $offset, $bits ) = @_;
    if( $offset > TWO_GB - 1 ) {
        $offset -= TWO_GB;
        $ref = \substr $$ref, ( TWO_GB * $bits ) / 8;
    }
    CORE::vec( $$ref, $offset, $bits );
}