Better document when -> can be used, closes #8386

lib/elixir/pages/Syntax Reference.md

@@ -118,7 +118,7 @@ Blocks are multiple Elixir expressions separated by newlines or semi-colons. A n
 
 ### Left to right arrow
 
-The left to right arrow (`->`) is used to establish a relationship between left and right. The left side may have zero, one, or more arguments; the right side is zero, one, or more expressions separated by new line. The `->` is always between one of the following terminators: `do`/`end`, `fn`/`end` or `(`/`)`.
+The left to right arrow (`->`) is used to establish a relationship between left and right, commonly referred as clauses. The left side may have zero, one, or more arguments; the right side is zero, one, or more expressions separated by new line. The `->` may appear one or more times between one of the following terminators: `do`/`end`, `fn`/`end` or `(`/`)`. When `->` is used, only other clauses are allowed between those terminators. Mixing clauses and regular expressions is invalid syntax.
 
 It is seen on `case` and `cond` constructs between `do`/`end`: