my @parts;

if ($msg->is_mime) {
    my @t_parts = $msg->parts();
    while (shift @t_parts) {
        if ($_->mime_type eq 'text/plain') {
             push @parts, $_;
             next;
        }
        if ($_->mime_type eq 'multipart/mixed' ||
            $_->mime_type eq 'multipart/alternative') {
             push @t_parts, $_->parts();
        }
    }
}