diff --git a/builtin-string.go b/builtin-string.go
index fc9abdf..1a690e3 100644
--- a/builtin-string.go
+++ b/builtin-string.go
@@ -12,6 +12,8 @@ import (
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/types"
 	"git.portale-stac.it/go-pkg/expr/types/array"
+	"git.portale-stac.it/go-pkg/expr/types/dict"
+	"git.portale-stac.it/go-pkg/expr/types/list"
 )
 
 const (
@@ -45,14 +47,24 @@ func joinStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result
 		if v, exists := args[kern.ParamItem]; exists {
 			argv := v.([]any)
 			if len(argv) == 1 {
-				if a, ok := argv[0].(*array.ArrayType); ok {
-					result, err = doJoinStr(name, sep, NewListIterator(a, nil))
-				} else if it, ok := argv[0].(kern.Iterator); ok {
+				var it kern.Iterator
+				if it, ok = argv[0].(kern.Iterator); !ok {
+					if a, ok := argv[0].(*array.ArrayType); ok {
+						it = NewArrayIteratorFromArray(a, nil)
+					} else if l, ok := argv[0].(*list.LinkedList); ok {
+						it = NewLinkedListIterator(l, nil)
+					} else if d, ok := argv[0].(*dict.DictType); ok {
+						if it, err = NewDictIteratorA(d, "none", "values"); err != nil {
+							return
+						}
+					}
+				}
+				if it != nil {
 					result, err = doJoinStr(name, sep, it)
 				} else if s, ok := argv[0].(string); ok {
 					result = s
 				} else {
-					err = kern.ErrInvalidParameterValue(name, kern.ParamItem, v)
+					err = kern.ErrInvalidParameterValue(name, kern.ParamItem, argv[0])
 				}
 			} else {
 				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
@@ -64,6 +76,30 @@ func joinStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result
 	return
 }
 
+// func joinStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+// 	if sep, ok := args[kern.ParamSeparator].(string); ok {
+// 		if v, exists := args[kern.ParamItem]; exists {
+// 			argv := v.([]any)
+// 			if len(argv) == 1 {
+// 				if a, ok := argv[0].(*array.ArrayType); ok {
+// 					result, err = doJoinStr(name, sep, NewListIterator(a, nil))
+// 				} else if it, ok := argv[0].(kern.Iterator); ok {
+// 					result, err = doJoinStr(name, sep, it)
+// 				} else if s, ok := argv[0].(string); ok {
+// 					result = s
+// 				} else {
+// 					err = kern.ErrInvalidParameterValue(name, kern.ParamItem, argv[0])
+// 				}
+// 			} else {
+// 				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
+// 			}
+// 		}
+// 	} else {
+// 		err = kern.ErrWrongParamType(name, kern.ParamSeparator, kern.TypeString, args[kern.ParamSeparator])
+// 	}
+// 	return
+// }
+
 func subStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var start = 0
 	var count = -1
diff --git a/t_expr_test.go b/t_expr_test.go
index f42c5c7..a38c697 100644
--- a/t_expr_test.go
+++ b/t_expr_test.go
@@ -35,7 +35,9 @@ func TestExpr(t *testing.T) {
 		/*  19 */ {`a=2; ${a}`, int64(2), nil},
 		/*  20 */ {`$_=2; $_`, int64(2), nil},
 		/*  21 */ {`$$`, dict.NewDict(map[any]any{"vars": dict.NewDict(nil), "funcs": dict.NewDict(nil)}), nil},
-		/*  22 */ {`
+		/*  22 */ {`builtin "string"; strJoin("-", [<"a", "b", "c">])`, nil, `strJoin(): invalid value [<"a", "b", "c">] (linked-list) for parameter "item"`},
+		/*  22 */ {`builtin ""`, nil, `strJoin(): invalid value [<"a", "b", "c">] (linked-list) for parameter "item"`},
+		/*  23 */ {`
 		ds={
 			"init":func(@end){@current=0 but true},
 			//"current":func(){current},
@@ -50,6 +52,6 @@ func TestExpr(t *testing.T) {
 	}
 	// t.Setenv("EXPR_PATH", ".")
 
-	// RunTestSuiteSpec(t, section, inputs, 19)
+	// RunTestSuiteSpec(t, section, inputs, 22)
 	RunTestSuite(t, section, inputs)
 }