diff --git a/builtin-iterator.go b/builtin-iterator.go
index d156525..5495453 100644
--- a/builtin-iterator.go
+++ b/builtin-iterator.go
@@ -17,26 +17,31 @@ const (
 	iterParamOperator = "operator"
 	iterParamVars     = "vars"
 	iterVarStatus     = "status"
+	iterParamStatus   = "status"
+	iterVarAbort      = "__abort"
 )
 
 func parseRunArgs(localCtx kern.ExprContext, args map[string]any) (it kern.Iterator, op kern.Functor, err error) {
 	var ok bool
 
 	if it, ok = args[kern.ParamIterator].(kern.Iterator); !ok {
-		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", kern.ParamIterator, args[kern.ParamIterator], kern.TypeName(args[kern.ParamIterator]))
+		// err = fmt.Errorf("parameter %q must be an iterator, passed %v [%s]", kern.ParamIterator, args[kern.ParamIterator], kern.TypeName(args[kern.ParamIterator]))
+		err = errBadParamType(kern.ParamIterator, kern.TypeIterator, args[kern.ParamIterator])
 		return
 	}
 
 	if args[iterParamOperator] != nil {
 		if op, ok = args[iterParamOperator].(kern.Functor); !ok || op == nil {
-			err = fmt.Errorf("paramter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], kern.TypeName(args[iterParamOperator]))
+			// err = fmt.Errorf("parameter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], kern.TypeName(args[iterParamOperator]))
+			err = errBadParamType(iterParamOperator, "function", args[iterParamOperator])
 			return
 		}
 	}
 
 	var vars *dict.DictType
 	if vars, ok = args[iterParamVars].(*dict.DictType); !ok && args[iterParamVars] != nil {
-		err = fmt.Errorf("paramter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], kern.TypeName(args[iterParamVars]))
+		// err = fmt.Errorf("parameter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], kern.TypeName(args[iterParamVars]))
+		err = errBadParamType(iterParamVars, kern.TypeDict, args[iterParamVars])
 		return
 	}
 
@@ -52,12 +57,21 @@ func parseRunArgs(localCtx kern.ExprContext, args map[string]any) (it kern.Itera
 	return
 }
 
+func errBadParamType(paramName, wantedType string, wantedValue any) error {
+	return fmt.Errorf("type of %q must be %s, passed %v [%s]", paramName, wantedType, wantedValue, kern.TypeName(wantedValue))
+}
+
+func abortFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	if status, provided := args[iterParamStatus]; provided {
+		ctx.UnsafeSetVar("@"+iterVarStatus, status)
+	}
+	ctx.UnsafeSetVar("@"+iterVarAbort, true)
+	return
+}
+
 func runFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var it kern.Iterator
-	var ok bool
 	var op kern.Functor
-	var v any
-	// var usingDefaultOp = false
 	var params map[string]any
 	var item any
 
@@ -68,14 +82,20 @@ func runFunc(ctx kern.ExprContext, name string, args map[string]any) (result any
 		return
 	}
 
+	localCtx.RegisterFunc("abort", kern.NewGolangFunctor(abortFunc), kern.TypeAny, []kern.ExprFuncParam{
+		kern.NewFuncParamFlagDef(iterParamStatus, kern.PfOptional, "aborted"),
+	})
+
+	params = map[string]any{kern.ParamIndex: 0, kern.ParamItem: nil}
 	for item, err = it.Next(); err == nil; item, err = it.Next() {
 		if op != nil {
-			params = map[string]any{kern.ParamIndex: it.Index(), kern.ParamItem: item}
-			if v, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
+			// params = map[string]any{kern.ParamIndex: it.Index(), kern.ParamItem: item}
+			params[kern.ParamIndex] = it.Index()
+			params[kern.ParamItem] = item
+			if _, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
 				break
-			} else {
-				var success bool
-				if success, ok = boolean.ToBool(v); !success || !ok {
+			} else if abortAny, exists := localCtx.GetVar(iterVarAbort); exists {
+				if abort, ok := boolean.ToBool(abortAny); ok && abort {
 					break
 				}
 			}
@@ -87,7 +107,7 @@ func runFunc(ctx kern.ExprContext, name string, args map[string]any) (result any
 	}
 	if err == nil {
 		if op == nil {
-			ctx.UnsafeSetVar(iterVarStatus, it.Count())
+			localCtx.UnsafeSetVar(iterVarStatus, it.Count())
 		}
 		result, _ = localCtx.GetVar(iterVarStatus)
 	}