diff --git a/ROADMAP.md b/ROADMAP.md
index 5e27bde..c335bab 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -3,7 +3,6 @@
 - [ ] Functions
 - [ ] imports
 - [ ] scopes of visibility
-- [ ] parallel tasks `{parallel:[..tasks]}`
 - [ ] types conversion
 - [ ] methods for arrays
 - [ ] methods for strings
@@ -12,5 +11,6 @@
 - [x] yaml support?
 - [ ] command execution function
 - [ ] function for random
+- [ ] delete variable
 
 and something else
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 768243f..877d4cb 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -285,14 +285,19 @@ impl Interpreter {
 
     fn define(&mut self, vars: &Map<String, Value>) -> Value {
         for (name, value) in vars {
-            match value {
-                Value::Object(_) => {
-                    let value = self.eval_node(value);
-                    self.vars.insert(name.to_string(), value);
-                }
-                _ => {
-                    self.vars.insert(name.to_string(), value.clone());
+            if !self.var_exists(&name) {
+                match value {
+                    Value::Object(_) => {
+                        let value = self.eval_node(value);
+                        self.vars.insert(name.to_string(), value);
+                    }
+                    _ => {
+                        self.vars.insert(name.to_string(), value.clone());
+                    }
                 }
+            } else {
+                self.error(&format!("The variable {} already exist, use assign", name));
+                panic!()
             }
         }
         Value::Null
@@ -311,9 +316,8 @@ impl Interpreter {
 
     fn assign(&mut self, vars: &Map<String, Value>) -> Value {
         for (name, value) in vars {
-            let var = self.vars.get(name);
-            match var {
-                Some(_) => match value {
+            if self.var_exists(&name) {
+                match value {
                     Value::Object(_) => {
                         let value = self.eval_node(value);
                         self.vars.insert(name.to_string(), value);
@@ -321,16 +325,22 @@ impl Interpreter {
                     _ => {
                         self.vars.insert(name.to_string(), value.clone());
                     }
-                },
-                None => {
-                    self.error(&format!("The variable {} does not exist", name));
-                    panic!();
                 }
+            } else {
+                self.error(&format!("The variable {} does not exist, use define", name));
+                panic!();
             }
         }
         Value::Null
     }
 
+    fn var_exists(&self, name: &String) -> bool {
+        match self.vars.get(name) {
+            Some(_) => true,
+            None => false,
+        }
+    }
+
     fn calc(&mut self, value: &Vec<Value>) -> Value {
         let op1 = &value[0];
         let operation = &value[1];