class Node {
    has Int $.data;
    has Node $.next = Nil;
}

class LinkedList {
    has Node $.head;

    method concat_list_str(Node $curr) {
    if !$curr {
        "";
    } elsif !$curr.next {
        $curr.data.Str
    } else {
      $curr.data.Str ~ "," ~ .concat_list_str($curr.next)
    }
    }

    method gist() {
    "[" ~ .concat_list_str($.head) ~ "]"
    }
}

my $list = LinkedList.new(head => Node.new(data => 1));
say $list;