diff --git a/regression/test034.expr b/regression/test034.expr
index de21748fa..dd898077e 100644
--- a/regression/test034.expr
+++ b/regression/test034.expr
@@ -14,5 +14,6 @@ for i:=0, i<x.length, i:=i+1 do
   x[i] := x[i]+2  
 od;
 
-printString (x)
+printString (x);
 
+printString (strcat ("abc", "def"))
diff --git a/src/Language.ml b/src/Language.ml
index 89f8b0b22..d68bbf535 100644
--- a/src/Language.ml
+++ b/src/Language.ml
@@ -85,8 +85,11 @@ module Builtin =
                    )         
     | "$length" -> (st, i, o, Some (Value.of_int (match List.hd args with Value.Array a -> List.length a | Value.String s -> String.length s)))
     | "$array"  -> (st, i, o, Some (Value.of_array args))
-    | s -> failwith (Printf.sprintf "Wow: %s\n" s)
-                     
+    | "strcat"  -> let [x; y] = args in
+                   (st, i, o, Some (Value.of_string @@ Value.to_string x ^ Value.to_string y))
+    | "isArray" -> let [a] = args in
+                   (st, i, o, Some (Value.of_int @@ match a with Array _ -> 1 | _ -> 0))
+       
   end
     
 (* Simple expressions: syntax and semantics *)
diff --git a/src/SM.ml b/src/SM.ml
index cd6e7a357..6ebf68b6a 100644
--- a/src/SM.ml
+++ b/src/SM.ml
@@ -6,8 +6,6 @@ open Language
 (* binary operator                 *) | BINOP   of string
 (* put a constant on the stack     *) | CONST   of int
 (* put a string on the stack       *) | STRING  of string                      
-(* read to stack                   *) | READ
-(* write from stack                *) | WRITE
 (* load a variable to the stack    *) | LD      of string
 (* store a variable from the stack *) | ST      of string
 (* store in an array               *) | STA     of string * int