diff --git a/src/cli-repl.rs b/src/cli-repl.rs
index 86ee31b..2d14046 100644
--- a/src/cli-repl.rs
+++ b/src/cli-repl.rs
@@ -1,4 +1,3 @@
-use std::f32::consts;
 use std::f64;
 use std::io::{self, StdoutLock, Write, stdout};
 use std::rc::Rc;
@@ -12,7 +11,6 @@ use libopenbirch::node::set::Set;
 use libopenbirch::node::string_node::StringNode;
 use libopenbirch::node::{Node, NodeEnum};
 use libopenbirch::parser::{Lexer, LexerError, Parser, ParserError};
-use raylib::ease::elastic_in;
 #[cfg(feature = "async")]
 use termion::AsyncReader;
 use termion::color;
@@ -382,6 +380,31 @@ fn benchmark(args: &Vec<Rc<NodeEnum>>, env: &mut Environment) -> Result<Rc<NodeE
     Ok(Set::new(vec![time_str, time_const, result]))
 }
 
+fn head(args: &Vec<Rc<NodeEnum>>, env: &mut Environment) -> Result<Rc<NodeEnum>, String> {
+    if args.len() != 1 {
+        Err(format!("Expected 1 argument but got {}", args.len()))?
+    }
+
+    let set = if let NodeEnum::Set(set) = args.first().unwrap().as_ref() {
+        set.get_values()
+    } else {
+        return Err(format!(
+            "Expected a Set but got a {}",
+            args.first().unwrap().type_str()
+        ));
+    };
+
+    let head = set.first().cloned().unwrap_or(Set::new(vec![]));
+    let len = set.len();
+    let tail = if len > 1 {
+        set[1..len].to_vec()
+    } else {
+        vec![]
+    };
+
+    Ok(Set::new(vec![head, Set::new(tail)]))
+}
+
 fn main() -> Result<(), io::Error> {
     let mut input = Input::new();
 
@@ -394,6 +417,7 @@ fn main() -> Result<(), io::Error> {
     env.define_native_function("get_float_precision", get_float_precision);
     env.define_native_function("set_float_precision", set_float_precision);
     env.define_native_function("map", map);
+    env.define_native_function("head", head);
     env.define_native_function("get", get);
     env.define_native_function("length", length);
     env.define_native_function("benchmark", benchmark);
diff --git a/src/lib/node/add.rs b/src/lib/node/add.rs
index 9349010..462ec1e 100644
--- a/src/lib/node/add.rs
+++ b/src/lib/node/add.rs
@@ -1,8 +1,11 @@
 use std::rc::Rc;
 
+use raylib::ffi::StopAutomationEventRecording;
 use rug::Float;
 
-use super::{Environment, Node, NodeEnum, Precedence, constant::Constant, set::Set};
+use super::{
+    Environment, Node, NodeEnum, Precedence, constant::Constant, set::Set, string_node::StringNode,
+};
 
 #[derive(Clone, Debug, PartialEq, PartialOrd)]
 pub struct Add {
@@ -44,6 +47,11 @@ impl Node for Add {
                 Ok(Set::new(values))
             }
 
+            // Concatenate strings
+            (NodeEnum::StringNode(s1), NodeEnum::StringNode(s2)) => {
+                Ok(StringNode::new(s1.get_value().clone() + s2.get_value()))
+            }
+
             _ => Ok(Rc::new(Add::new(evaluated_left, evaluated_right).into())),
         }
     }
diff --git a/src/lib/node/assign.rs b/src/lib/node/assign.rs
index f2bdc14..962013b 100644
--- a/src/lib/node/assign.rs
+++ b/src/lib/node/assign.rs
@@ -1,6 +1,6 @@
 use std::rc::Rc;
 
-use super::{Environment, Node, NodeEnum, Precedence, empty::Empty};
+use super::{Environment, Node, NodeEnum, Precedence, empty::Empty, symbol};
 
 #[derive(Debug, Clone, PartialEq, PartialOrd)]
 pub struct Assign {
@@ -10,23 +10,70 @@ pub struct Assign {
 
 impl Node for Assign {
     fn evaluate(&self, env: &mut Environment) -> Result<Rc<NodeEnum>, String> {
-        if let NodeEnum::Symbol(symbol) = self.left.as_ref() {
-            let name = env
-                .id_to_str(&symbol.get_value())
-                .expect("Unknown symbol")
-                .clone();
-            let right = self.right.evaluate(env)?;
+        match self.left.as_ref() {
+            NodeEnum::Symbol(symbol) => {
+                let name = env
+                    .id_to_str(&symbol.get_value())
+                    .expect("Unknown symbol")
+                    .clone();
+                let right = self.right.evaluate(env)?;
 
-            env.insert(symbol.get_value(), right.clone());
-            Ok(Empty::new(format!(
-                "{name} := {}",
-                right.as_string(Some(env))
-            )))
-        } else {
-            Err(format!(
-                "Cannot assign to a {}",
-                self.left.as_string(Some(env))
-            ))
+                env.insert(symbol.get_value(), right.clone());
+                Ok(Empty::new(format!(
+                    "{name} := {}",
+                    right.as_string(Some(env))
+                )))
+            }
+
+            NodeEnum::Set(set) => {
+                // Check if every element of the set is a symbol
+                let values = set.get_values();
+
+                if values.len() == 0 {
+                    return Err(format!("Cannot assign to an empty Set"));
+                }
+
+                let mut symbols = Vec::with_capacity(values.len());
+                for node in values {
+                    if let NodeEnum::Symbol(symbol) = node.as_ref() {
+                        symbols.push(symbol);
+                    } else {
+                        return Err(format!("Cannot assign to a {}", node.type_str()));
+                    }
+                }
+
+                // Evaluate right hand side and check that it is a set of the same size
+                let right = self.right.evaluate(env)?;
+
+                if let NodeEnum::Set(set) = right.as_ref() {
+                    let values = set.get_values();
+                    if values.len() != symbols.len() {
+                        return Err(format!(
+                            "Expected rhs with {} elements but got {}",
+                            symbols.len(),
+                            values.len()
+                        ));
+                    }
+
+                    for (symbol,value) in symbols.iter().zip(values.into_iter()) {
+                        env.insert(symbol.get_value(), value.clone());
+                    }
+
+                    Ok(Empty::new(format!(
+                        "[{}] := {}",
+                        symbols
+                            .iter()
+                            .map(|x| env.id_to_str(&x.get_value()).unwrap().clone())
+                            .reduce(|x, acc| format!("{x}, {acc}"))
+                            .unwrap(),
+                        right.as_string(Some(env))
+                    )))
+                } else {
+                    return Err(format!("Cannot unpack {} for assignment", right.type_str()));
+                }
+            }
+
+            _ => Err(format!("Cannot assign to a {}", self.left.type_str())),
         }
     }
 
diff --git a/src/lib/node/call.rs b/src/lib/node/call.rs
index 668d9bf..8f74f8a 100644
--- a/src/lib/node/call.rs
+++ b/src/lib/node/call.rs
@@ -66,7 +66,14 @@ impl Node for Call {
                 fargs.iter().zip(&arguments).for_each(|(symbol, value)| {
                     env.insert(symbol.get_value(), value.clone());
                 });
-                let ev = body.evaluate(env)?;
+                let ev = body.evaluate(env);
+
+                if ev.is_err() {
+                    env.pop_stack()?;
+                    return ev;
+                }
+
+                let ev = ev?;
 
                 // Return evaluated return value for function
                 Ok(match ev.as_ref() {