In the inline code, replace
(put. env val) with
(.put env val).
In the code block, replace
But that won't solve the exception. It seems like you're hitting either https://clojure.atlassian.net/browse/CLJ-1243 (even though the description is not entirely the same, the root cause might be) or something very similar, and I can also reproduce it.
In order to fix it, add a type annotation:
(.put ^java.util.Map environment env val).