add array shadow

std.isbpl

@@ -423,3 +423,29 @@ func struppercase {
 func main {
     pop 0
 }
+
+func aadd {
+    def arr2 =arr2
+    def arr1 =arr1
+    
+    def new arr1 alen arr2 alen + anew =new
+    arr1 new 0 0         arr1 alen acopy =new
+    arr2 new 0 arr1 alen arr2 alen acopy =new
+
+    new
+}
+
+def TYPE_SHADOW "shadow" mktype =TYPE_SHADOW
+
+func [ {
+    TYPE_ARRAY TYPE_SHADOW settype
+}
+
+func ] {
+    "create an array until arrayshadow is found" #
+    def array 0 anew =array
+    while { dup [ eq not } {
+        1 anewput array aadd =array
+    }
+    pop array
+}