diff --git a/README.md b/README.md
index cf514c5..56511eb 100644
--- a/README.md
+++ b/README.md
@@ -4,15 +4,15 @@ Yet another Push-based genetic programming system in Clojure.
 
 ## Usage
 
-To run PushGP on the default genetic programming problem 
-from a REPL, load propel.core into your REPL (i.e. `lein repl`), 
-and run `(-main)`.
+To run PushGP from a REPL, load propel.core into your REPL (i.e. `lein repl`), 
+and run `-main` with arguments including, first, the problem name, for example:
+`(-main 'simple-regression)` or `(-main 'simple-regression :population-size 100)`.
 
-To run PushGP on the default genetic programming problem from 
-command line, execute `lein run`. Command-line arguments may 
-be provided to override the defaults specified in `-main`, for 
-example, `lein run :population-size 100`. You can use something 
-like `lein run | tee outfile` to send output both to the terminal 
+To run PushGP on the genetic programming problem p from the 
+command line, execute `lein run p`. For example `lein run simple-regression`. Additional command-line arguments may 
+be provided to override the default key/value pairs specified in `-main`, for 
+example, `lein run simple-regression :population-size 100`. You can use something 
+like `lein run simple-regression | tee outfile` to send output both to the terminal 
 and to `outfile`.
 
 ## CLJS Usage
diff --git a/src/propeller/core.cljc b/src/propeller/core.cljc
index 720184f..d24adb8 100755
--- a/src/propeller/core.cljc
+++ b/src/propeller/core.cljc
@@ -33,6 +33,7 @@
          :variation               {:umad 0.5 :crossover 0.5}
          :elitism                 false}
         (apply hash-map
-               (map read-string (rest args))))
+               (map #(if (string? %) (read-string %) %)
+                    (rest args))))
       [:error-function]
       identity)))