diff --git a/cmdlang/eval.go b/cmdlang/eval.go
index 38eb13b..828b526 100644
--- a/cmdlang/eval.go
+++ b/cmdlang/eval.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"github.com/lmika/gopkgs/fp/slices"
 	"strconv"
 	"strings"
 )
@@ -86,14 +85,32 @@ func (e evaluator) evalCmd(ctx context.Context, ec *evalCtx, currentStream strea
 }
 
 func (e evaluator) evalInvokable(ctx context.Context, ec *evalCtx, currentStream stream, ast *astCmd, cmd invokable) (object, error) {
-	args, err := slices.MapWithError(ast.Args, func(a astCmdArg) (object, error) {
-		return e.evalArg(ctx, ec, a)
-	})
-	if err != nil {
-		return nil, err
+	var (
+		pargs   listObject
+		kwargs  map[string]*listObject
+		argsPtr *listObject
+	)
+
+	argsPtr = &pargs
+	for _, arg := range ast.Args {
+		if ident := arg.Ident; ident != nil && (*ident)[0] == '-' {
+			// Arg switch
+			if kwargs == nil {
+				kwargs = make(map[string]*listObject)
+			}
+
+			argsPtr = &listObject{}
+			kwargs[(*ident)[1:]] = argsPtr
+		} else {
+			ae, err := e.evalArg(ctx, ec, arg)
+			if err != nil {
+				return nil, err
+			}
+			argsPtr.Append(ae)
+		}
 	}
 
-	invArgs := invocationArgs{ec: ec, inst: e.inst, args: args, currentStream: currentStream}
+	invArgs := invocationArgs{ec: ec, inst: e.inst, args: pargs, kwargs: kwargs, currentStream: currentStream}
 
 	if currentStream != nil {
 		if si, ok := cmd.(streamInvokable); ok {
diff --git a/cmdlang/objs.go b/cmdlang/objs.go
index b08ed21..f71074d 100644
--- a/cmdlang/objs.go
+++ b/cmdlang/objs.go
@@ -14,6 +14,10 @@ type object interface {
 
 type listObject []object
 
+func (lo *listObject) Append(o object) {
+	*lo = append(*lo, o)
+}
+
 func (s listObject) String() string {
 	return fmt.Sprintf("%v", []object(s))
 }
@@ -152,6 +156,7 @@ type invocationArgs struct {
 	ec            *evalCtx
 	currentStream stream
 	args          []object
+	kwargs        map[string]*listObject
 }
 
 func (ia invocationArgs) expectArgn(x int) error {
diff --git a/cmdlang/userbuiltin.go b/cmdlang/userbuiltin.go
index ec19b0d..7e825f3 100644
--- a/cmdlang/userbuiltin.go
+++ b/cmdlang/userbuiltin.go
@@ -16,32 +16,35 @@ func (ca CallArgs) Bind(vars ...interface{}) error {
 	}
 
 	for i, v := range vars {
-		switch t := v.(type) {
-		case *string:
-			tv, err := ca.args.stringArg(i)
-			if err != nil {
-				return err
-			}
-			*t = tv
-		}
-
-		// Check for proxy object
-		if po, ok := ca.args.args[i].(proxyObject); ok {
-			poValue := reflect.ValueOf(po.p)
-			argValue := reflect.ValueOf(v)
-
-			if argValue.Type().Kind() != reflect.Pointer {
-				continue
-			} else if !poValue.Type().AssignableTo(argValue.Elem().Type()) {
-				continue
-			}
-
-			argValue.Elem().Set(poValue)
+		if err := bindArg(v, ca.args.args[i]); err != nil {
+			return err
 		}
 	}
 	return nil
 }
 
+func (ca CallArgs) HasSwitch(name string) bool {
+	if ca.args.kwargs == nil {
+		return false
+	}
+
+	_, ok := ca.args.kwargs[name]
+	return ok
+}
+
+func (ca CallArgs) BindSwitch(name string, val interface{}) error {
+	if ca.args.kwargs == nil {
+		return nil
+	}
+
+	vars, ok := ca.args.kwargs[name]
+	if !ok || len(*vars) != 1 {
+		return nil
+	}
+
+	return bindArg(val, (*vars)[0])
+}
+
 func (inst *Inst) SetBuiltin(name string, fn func(ctx context.Context, args CallArgs) (any, error)) {
 	inst.rootEC.addCmd(name, userBuiltin{fn: fn})
 }
@@ -58,3 +61,25 @@ func (u userBuiltin) invoke(ctx context.Context, args invocationArgs) (object, e
 
 	return fromGoValue(v)
 }
+
+func bindArg(v interface{}, arg object) error {
+	switch t := v.(type) {
+	case *string:
+		*t = arg.String()
+	}
+
+	// Check for proxy object
+	if po, ok := arg.(proxyObject); ok {
+		poValue := reflect.ValueOf(po.p)
+		argValue := reflect.ValueOf(v)
+
+		if argValue.Type().Kind() != reflect.Pointer {
+			return nil
+		} else if !poValue.Type().AssignableTo(argValue.Elem().Type()) {
+			return nil
+		}
+
+		argValue.Elem().Set(poValue)
+	}
+	return nil
+}
diff --git a/cmdlang/userbuiltin_test.go b/cmdlang/userbuiltin_test.go
index 5f42016..5c93e1a 100644
--- a/cmdlang/userbuiltin_test.go
+++ b/cmdlang/userbuiltin_test.go
@@ -2,6 +2,7 @@ package cmdlang_test
 
 import (
 	"context"
+	"strings"
 	"testing"
 
 	"github.com/lmika/cmdlang-proto/cmdlang"
@@ -26,6 +27,48 @@ func TestInst_SetBuiltin(t *testing.T) {
 		assert.Equal(t, "Hello, World", res)
 	})
 
+	t.Run("simple builtin with optional switches and strings", func(t *testing.T) {
+		inst := cmdlang.New()
+		inst.SetBuiltin("add2", func(ctx context.Context, args cmdlang.CallArgs) (any, error) {
+			var x, y, sep string
+
+			if err := args.BindSwitch("sep", &sep); err != nil {
+				return nil, err
+			}
+			if err := args.BindSwitch("left", &x); err != nil {
+				return nil, err
+			}
+			if err := args.BindSwitch("right", &y); err != nil {
+				return nil, err
+			}
+
+			v := x + sep + y
+			if args.HasSwitch("upcase") {
+				v = strings.ToUpper(v)
+			}
+
+			return v, nil
+		})
+
+		tests := []struct {
+			descr string
+			expr  string
+			want  string
+		}{
+			{"plain eval", `add2 -sep ", " -right "world" -left "Hello"`, "Hello, world"},
+			{"swap 1", `add2 -right "right" -left "left" -sep ":"`, "left:right"},
+			{"swap 2", `add2 -left "left" -sep ":" -right "right" -upcase`, "LEFT:RIGHT"},
+		}
+
+		for _, tt := range tests {
+			t.Run(tt.descr, func(t *testing.T) {
+				res, err := inst.Eval(context.Background(), tt.expr)
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			})
+		}
+	})
+
 	t.Run("builtin return proxy object", func(t *testing.T) {
 		type pair struct {
 			x, y string