diff --git a/src/interpreter.rs b/src/interpreter.rs
index cdcf83f..ededc52 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -1,10 +1,11 @@
-use std::collections::HashMap;
+use std::{collections::HashMap, rc::Rc};
 
 use crate::{parser::{Expr, BinOpType, UnOpType, Ast, Stmt, parse}, lexer::lex};
 
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Value {
     I64(i64),
+    Str(Rc<String>),
 }
 
 pub struct Interpreter {
@@ -50,6 +51,9 @@ impl Interpreter {
                         match self.resolve_expr(condition) {
                             Value::I64(val) if val == 0 => break,
                             Value::I64(_) => (),
+
+                            Value::Str(text) if text.is_empty() => break,
+                            Value::Str(_) => (),
                         }
 
                         // Execute loop body
@@ -70,6 +74,7 @@ impl Interpreter {
     fn resolve_expr(&mut self, expr: &Expr) -> Value {
         match expr {
             Expr::I64(val) => Value::I64(*val),
+            Expr::Str(name) => Value::Str(name.clone()),
             Expr::BinOp(bo, lhs, rhs) => self.resolve_binop(bo, &lhs, &rhs),
             Expr::UnOp(uo, val) => self.resolve_unop(uo, &val),
             Expr::Ident(name) => {
@@ -118,7 +123,7 @@ impl Interpreter {
                 BinOpType::Le => Value::I64(if lhs <= rhs { 1 } else { 0 }),
                 BinOpType::Assign => unreachable!(),
             },
-            // _ => panic!("Value types are not compatible"),
+            _ => panic!("Value types are not compatible"),
         }
     }
 
@@ -128,6 +133,7 @@ impl Interpreter {
             Value::I64(val) => match uo {
                 UnOpType::Neg => Value::I64(-val),
             }
+            _ => panic!("Invalid unary operation for type"),
         }
     }
 
diff --git a/src/lexer.rs b/src/lexer.rs
index 75b15d7..25c3961 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -7,6 +7,9 @@ pub enum Token {
     /// Integer literal (64-bit)
     I64(i64),
 
+    /// String literal ("Some string")
+    Str(String),
+
     /// Left parenthesis ('(')
     LParen,
 
@@ -180,6 +183,46 @@ impl<'a> Lexer<'a> {
                 '}' => tokens.push(Token::RBrace),
                 '$' => tokens.push(Token::Dollar),
 
+                '"' => {
+                    let mut text = String::new();
+
+                    let mut escape = false;
+
+                    // Do as long as a next char exists and it is not '"'
+                    loop {
+                        if escape {
+                            escape = false;
+
+                            match self.next() {
+                                Some('\\') => text.push('\\'),
+                                Some('n') => text.push('\n'),
+                                Some('r') => text.push('\r'),
+                                Some('t') => text.push('\t'),
+                                ch => panic!("Invalid string escape: '{:?}'", ch),
+                            }
+
+                        } else {
+                            match self.peek() {
+                                Some('"') => {
+                                    self.next();
+                                    break;
+                                }
+                                Some('\\') => {
+                                    self.next();
+                                    escape = true;
+                                }
+                                None => panic!("String is never terminated (missing '\"')"),
+
+                                _ => text.push(self.next().unwrap()),
+                            }
+                        }
+                    }
+
+
+
+                    tokens.push(Token::Str(text));
+                }
+
                 'a'..='z' | 'A'..='Z' | '_' => {
                     let mut ident = String::from(ch);
 
diff --git a/src/parser.rs b/src/parser.rs
index ac51b42..5c492a8 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,4 +1,4 @@
-use std::iter::Peekable;
+use std::{iter::Peekable, rc::Rc};
 
 use crate::lexer::Token;
 
@@ -82,6 +82,8 @@ pub enum Stmt {
 pub enum Expr {
     /// Integer literal (64-bit)
     I64(i64),
+    /// String literal
+    Str(Rc<String>),
     /// Identifier (variable name)
     Ident(String),
     /// Binary operation. Consists of type, left hand side and right hand side
@@ -93,6 +95,7 @@ pub enum Expr {
 /*
 ## Grammar
 ### Expressions
+LITERAL = I64 | Str
 expr_primary = LITERAL | IDENT | "(" expr ")" | "-" expr_primary
 expr_mul = expr_primary (("*" | "/" | "%") expr_primary)*
 expr_add = expr_mul (("+" | "-") expr_mul)*
@@ -265,6 +268,8 @@ impl<T: Iterator<Item = Token>> Parser<T> {
         match self.next() {
             Token::I64(val) => Expr::I64(val),
 
+            Token::Str(text) => Expr::Str(text.into()),
+
             Token::Ident(name) => Expr::Ident(name),
 
             Token::LParen => {