diff --git a/go.mod b/go.mod
index b65ae1b..b7b4cb6 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,7 @@ require (
 	github.com/chzyer/readline v1.5.1
 	github.com/lmika/gopkgs v0.0.0-20240408110817-a02f6fc67d1f
 	github.com/stretchr/testify v1.10.0
+	lmika.dev/pkg/modash v0.0.0-20250619112300-0be0b6b35b1b
 )
 
 require (
@@ -17,5 +18,4 @@ require (
 	go.abhg.dev/goldmark/frontmatter v0.2.0 // indirect
 	golang.org/x/sys v0.0.0-20220310020820-b874c991c1a5 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	lmika.dev/pkg/modash v0.0.0-20250619112300-0be0b6b35b1b // indirect
 )
diff --git a/go.sum b/go.sum
index a9528c9..99a7730 100644
--- a/go.sum
+++ b/go.sum
@@ -22,6 +22,7 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/yuin/goldmark v1.7.8 h1:iERMLn0/QJeHFhxSt3p6PeN9mGnvIKSpG9YYorDMnic=
 github.com/yuin/goldmark v1.7.8/go.mod h1:uzxRWxtg69N339t3louHJ7+O03ezfj6PlliRlaOzY1E=
diff --git a/ucl/builtins/fns_test.go b/ucl/builtins/fns_test.go
new file mode 100644
index 0000000..a7fe418
--- /dev/null
+++ b/ucl/builtins/fns_test.go
@@ -0,0 +1,31 @@
+package builtins_test
+
+import (
+	"context"
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"ucl.lmika.dev/ucl"
+	"ucl.lmika.dev/ucl/builtins"
+)
+
+func TestFns_Uni(t *testing.T) {
+	tests := []struct {
+		descr string
+		eval  string
+		want  any
+	}{
+		{descr: "uni 1", eval: `s = fns:uni add 2 ; $s 3`, want: 5},
+		{descr: "uni 2", eval: `s = fns:uni (proc { |x| add $x 1 }) ; $s 3`, want: 4},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.descr, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Fns()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, res)
+		})
+	}
+}
diff --git a/ucl/builtins/lists.go b/ucl/builtins/lists.go
index 4e70095..20df5b2 100644
--- a/ucl/builtins/lists.go
+++ b/ucl/builtins/lists.go
@@ -10,12 +10,45 @@ func Lists() ucl.Module {
 	return ucl.Module{
 		Name: "lists",
 		Builtins: map[string]ucl.BuiltinHandler{
-			"first": listFirst,
-			"uniq":  listUniq,
+			"append": listAppend,
+			"first":  listFirst,
+			"batch":  listBatch,
+			"uniq":   listUniq,
 		},
 	}
 }
 
+func listAppend(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		what ucl.Object
+		item ucl.Object
+	)
+
+	if err := args.Bind(&what); err != nil {
+		return nil, err
+	}
+
+	if what == nil {
+		what = ucl.NewListObject()
+	}
+
+	t, ok := what.(ucl.ModListable)
+	if !ok {
+		return nil, errors.New("expected mutable list")
+	}
+
+	for args.NArgs() > 0 {
+		if err := args.Bind(&item); err != nil {
+			return nil, err
+		}
+		if err := t.Insert(-1, item); err != nil {
+			return nil, err
+		}
+	}
+
+	return t, nil
+}
+
 func listFirst(ctx context.Context, args ucl.CallArgs) (any, error) {
 	var (
 		what  ucl.Object
@@ -125,3 +158,34 @@ func listUniq(ctx context.Context, args ucl.CallArgs) (any, error) {
 
 	return found, nil
 }
+
+func listBatch(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		what      ucl.Object
+		groupSize int
+	)
+
+	if err := args.Bind(&what, &groupSize); err != nil {
+		return nil, err
+	}
+
+	if groupSize <= 0 {
+		return nil, errors.New("group size must be > 0")
+	}
+
+	groups := ucl.NewListObject()
+	var thisGroup *ucl.ListObject
+
+	if err := eachListOrIterItem(ctx, what, func(idx int, v ucl.Object) error {
+		if thisGroup == nil || thisGroup.Len() == groupSize {
+			thisGroup = ucl.NewListObject()
+			groups.Append(thisGroup)
+		}
+		thisGroup.Append(v)
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	return groups, nil
+}
diff --git a/ucl/builtins/lists_test.go b/ucl/builtins/lists_test.go
index 72ccf65..cf65a2c 100644
--- a/ucl/builtins/lists_test.go
+++ b/ucl/builtins/lists_test.go
@@ -8,6 +8,44 @@ import (
 	"ucl.lmika.dev/ucl/builtins"
 )
 
+func TestLists_Append(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "append 1", eval: `lists:append [1 2 3] 4`, want: []any{1, 2, 3, 4}},
+		{desc: "append 2", eval: `lists:append [1 2 3] 4 5 6`, want: []any{1, 2, 3, 4, 5, 6}},
+		{desc: "append 3", eval: `lists:append [] 1 2 3`, want: []any{1, 2, 3}},
+		{desc: "append 4", eval: `lists:append () 1 2 3`, want: []any{1, 2, 3}},
+		{desc: "append 5", eval: `lists:append [1 2 3]`, want: []any{1, 2, 3}},
+		{desc: "append 6", eval: `l = [] ; lists:append $l 1 2 3 ; $l`, want: []any{1, 2, 3}},
+		{desc: "append 7", eval: `l = [1 2 3] ; lists:append $l [4 5 6] ; $l`, want: []any{1, 2, 3, []any{4, 5, 6}}},
+		{desc: "append 8", eval: `lists:append (seq 3 | itrs:from | itrs:to-list) 4 5 6`, want: []any{0, 1, 2, 4, 5, 6}},
+
+		{desc: "err 1", eval: `lists:append "asa" 1`, wantErr: true},
+		{desc: "err 2", eval: `lists:append 123 1`, wantErr: true},
+		{desc: "err 3", eval: `lists:append [:] 1`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Itrs()),
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
 func TestLists_First(t *testing.T) {
 	tests := []struct {
 		desc    string
@@ -45,6 +83,42 @@ func TestLists_First(t *testing.T) {
 	}
 }
 
+func TestLists_Batch(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "batch 1", eval: `lists:batch [1 2 3 4 5] 2`, want: []any{[]any{1, 2}, []any{3, 4}, []any{5}}},
+		{desc: "batch 2", eval: `lists:batch [1 2 3 4] 2`, want: []any{[]any{1, 2}, []any{3, 4}}},
+		{desc: "batch 3", eval: `lists:batch [1 2 3 4 5] 3`, want: []any{[]any{1, 2, 3}, []any{4, 5}}},
+		{desc: "batch 4", eval: `lists:batch [1 2 3 4 5] 12`, want: []any{[]any{1, 2, 3, 4, 5}}},
+		{desc: "batch 5", eval: `lists:batch [1 2 3 4 5] 1`, want: []any{[]any{1}, []any{2}, []any{3}, []any{4}, []any{5}}},
+		{desc: "batch 6", eval: `lists:batch [1] 12`, want: []any{[]any{1}}},
+		{desc: "batch 7", eval: `lists:batch [] 12`, want: []any{}},
+
+		{desc: "err 1", eval: `lists:batch [1 2 3] -3`, wantErr: true},
+		{desc: "err 2", eval: `lists:batch [1 2 3] 0`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Itrs()),
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
 func TestLists_Uniq(t *testing.T) {
 	tests := []struct {
 		desc    string