Is there a list of the syntax sugar we have so far?
I remember being told about table!key being equivalent to (table key), and : is used to string functions together (although I keep forgetting it works from inside out).
I'm not sure what . offers, except that you can do *(3 . + . 5) with it. The example of foo.bar being equal to (foo bar) isn't helping much either ;)
Note that you can also use : to compose multiple functions.
The Anarki also has, if you include "ssyntaxes.arc":
11. x..y, which is the same as (range x y), and x..y..z, which is the same as (range x y z) (a range from x to y with step size z).
12. f//g, which is the same as (orf f g); this returns a function where ((orf f g) x y ...) is equivalent to (or (f x y ...) (g x y ...)). This can be used with as many functions as you want.
13. f&&g, which is like f//g but uses andf instead of orf, so the function is equivalent to (and (f x y ...) ...).
14. typ?, which returns the function (fn (x) (isa x 'typ)).
15. User-definable ssyntax, so you can add your own!
Also, note that ssyntax only works with variables and integers, not with literal lists or function calls.
And your example of using . for infix is actually a holdover from mzscheme, and not used anywhere particularly; its existence in Arc seems to be accidental.