Clojure uses vector syntax for lambda arguments. `read` sees a vector. What comes out of eval is a lambda. Does a Vector get built in the process? You'd have to

Clojure uses vector syntax for lambda arguments. `read` sees a vector. What comes out of eval is a lambda. Does a Vector get built in the process? You'd have to check, my bet would be that the argument list spends a little while as a Java Array, for performance reasons, but that a Clojure Vector is not actually constructed.