Syntax is hard. In general I think that adding a simple numbered argument access for blocks makes sense, and something like swifts $ syntax would look pretty natural, ie:

``` books.map { $0.title } ```

In the Ruby lang discussion on this they go through a dozen different possible syntaxes and they all have issues -- for example the $ is problematic because Ruby currently uses these for global variables.

Even so, IMO using the `@` symbol for this will make the language harder to learn. It's not a very nice thing to have syntax that is almost ambiguous to the human.

``` books.map { @prefix + @1.author } ```

I teach Ruby to a lot of engineers (of all different experience levels), and one of the nice things is that it's so easy to pick up and be productive quickly. But there are bits where it takes some practice, and I'm not looking forward to telling people, "The at sign means it's an instance variable. Well, except if you're in a block and it's @1 or @2 or something, in which case it's a positional argument." Oof.