ato

clojure.core/refer is relatively heavyweight.  It gets called 7 times during Clojure
 startup (4 times in 1.3.0).  There's potential to shave off 10% of the startup time
by improving it.  Probably even more for projects with a large number of small
namespaces.

This is just a quick experiment to see what's possible, it would need much refining.
It's not thread safe, doesn't print warnings and could probably be written more
elegantly.

java -Xbootclasspath/a:clojure.jar -cp clojure.jar clojure.main -e "(System/exit 0)"