This once again does NOT compile. I've done work on macros; they don't work yet..

unit-tests/allocation-tests/grep.bb

@@ -0,0 +1,19 @@
+#!/home/simon/bin/bb
+
+(require '[clojure.java.io :as io])
+(import '[java.lang ProcessBuilder$Redirect])
+
+(defn grep [input pattern]
+  (let [proc (-> (ProcessBuilder. ["grep" pattern])
+                 (.redirectOutput ProcessBuilder$Redirect/INHERIT)
+                 (.redirectError ProcessBuilder$Redirect/INHERIT)
+                 (.start))
+        proc-input (.getOutputStream proc)]
+    (with-open [w (io/writer proc-input)]
+      (binding [*out* w]
+        (print input)
+        (flush)))
+    (.waitFor proc)
+    nil))
+
+(grep "hello\nbye\n" "e")