diff --git a/builtin-base.go b/builtin-base.go
index 537be8b..30e57c5 100644
--- a/builtin-base.go
+++ b/builtin-base.go
@@ -211,6 +211,25 @@ func evalFunc(ctx ExprContext, name string, args map[string]any) (result any, er
 	return
 }
 
+func varFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var varName string
+	var ok bool
+
+	if varName, ok = args[ParamName].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamName, TypeString, args[ParamName])
+	}
+
+	if result, ok = args[ParamValue]; ok && result != nil {
+		ctx.GetParent().UnsafeSetVar(varName, result)
+		// } else {
+		// 	err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		// }
+	} else if result, ok = ctx.GetVar(varName); !ok {
+		err = ErrUnknownVar(name, varName)
+	}
+	return
+}
+
 //// import
 
 func ImportBuiltinsFuncs(ctx ExprContext) {
@@ -240,6 +259,11 @@ func ImportBuiltinsFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("eval", NewGolangFunctor(evalFunc), TypeAny, []ExprFuncParam{
 		NewFuncParam(ParamSource),
 	})
+
+	ctx.RegisterFunc("var", NewGolangFunctor(varFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamName),
+		NewFuncParamFlagDef(ParamValue, PfDefault, nil),
+	})
 }
 
 func init() {
diff --git a/common-errors.go b/common-errors.go
index f103c2c..f0b6973 100644
--- a/common-errors.go
+++ b/common-errors.go
@@ -80,6 +80,10 @@ func ErrUnknownParam(funcName, paramName string) error {
 	return fmt.Errorf("%s(): unknown parameter %q", funcName, paramName)
 }
 
+func ErrUnknownVar(funcName, varName string) error {
+	return fmt.Errorf("%s(): unknown variable %q", funcName, varName)
+}
+
 // --- Operator errors
 
 func ErrLeftOperandMustBeVariable(leftTerm, opTerm *term) error {