Example from the OP:

        fun to-celsius(f):
          (f - 32) * (5 / 9)
        end

What's the justification for allowing the use of hyphens/dashes in reference names, when underscores would seemingly provide the same purpose? One of the most common problems I notice in newbie code is inconsistency in using whitespace, e.g. `a-b` vs `a - b`, though in that situation, for Python and virtually every other language I've used, those both result in subtracting b from a. But in Pyret, it seems that `a-b` would be interpreted as a reference? That seems needlessly confusing for no benefit in readability over using snakecase.

Beginners frequently have issues with grammar, that is, they are pretty much unaware of it when trying to figure out the many other things they have to learn about programming. Even in SQL, I forget that it must be quite confusing for beginners to parse out the meaning of the `` in something as simple as:

     SELECT mytable.*, (a * b) AS myproduct, 
          COUNT(*) AS the count
     FROM mytable ...

Doesn't seem worth it to make the hyphen, which is so frequently associated with subtraction and negative numbers, have just a decorative meaning when used between word tokens (as opposed to subtraction of values represented by variables).