diff --git a/lyt/src/ast.rs b/lyt/src/ast.rs
index e4d1177..efbacf0 100644
--- a/lyt/src/ast.rs
+++ b/lyt/src/ast.rs
@@ -14,3 +14,5 @@ pub enum Expression {
     Integer(i64),
     Unit,
 }
+
+impl Expression {}
diff --git a/lyt/src/cli.rs b/lyt/src/cli.rs
index 433e464..93ba42f 100644
--- a/lyt/src/cli.rs
+++ b/lyt/src/cli.rs
@@ -1,4 +1,12 @@
-use std::str::FromStr;
+use std::{
+    io::{self, Write},
+    str::FromStr,
+};
+
+use crate::{
+    lexer::{self, Lexer, Source, Token},
+    parser::Parser,
+};
 
 struct GlobalArgs {
     subcommand: Option<Subcommand>,
@@ -44,7 +52,7 @@ fn usage(exit_code: i32) -> ! {
 
 fn parse_global_args() -> Result<GlobalArgs, ParseArgsError> {
     let mut subcommand = None;
-    let mut args = std::env::args();
+    let mut args = std::env::args().skip(1);
 
     while let Some(arg) = args.next() {
         match arg.as_str() {
@@ -61,6 +69,46 @@ fn parse_global_args() -> Result<GlobalArgs, ParseArgsError> {
     return Ok(GlobalArgs { subcommand });
 }
 
-pub fn run() -> crate::Result<()> {
-    Ok(())
+fn repl() -> ! {
+    println!("lytlang repl (^D to stop)");
+    print!("> ");
+    std::io::stdout().flush().expect("failed to flush stdout");
+    let mut iter = std::io::stdin().lines().enumerate().into_iter();
+    while let Some((i, l)) = iter.next() {
+        let s = match &l {
+            Ok(s) => s.as_str(),
+            Err(e) => {
+                eprintln!("error reading line from stdin: {}", e);
+                continue;
+            }
+        };
+        let tokens = match Lexer::new(s, Source::Repl(i)).collect() {
+            Ok(tokens) => tokens,
+            Err(e) => {
+                eprintln!("error lexing input: {:?}", e);
+                continue;
+            }
+        };
+        match Parser::default().parse(tokens) {
+            Ok(expr) => println!("< {:?}", expr),
+            Err(e) => {
+                eprintln!("error parsing tokens: {:?}", e);
+                continue;
+            }
+        }
+        println!("> ");
+        std::io::stdout().flush().expect("failed to flush stdout");
+    }
+    std::process::exit(0);
+}
+
+pub fn run() -> crate::Result<()> {
+    match parse_global_args()?.subcommand {
+        Some(Subcommand::Repl) => repl(),
+        Some(Subcommand::Help) => usage(0),
+        None => {
+            println!("no subcommand specified");
+            usage(1)
+        }
+    }
 }
diff --git a/lyt/src/lexer.rs b/lyt/src/lexer.rs
index c5e67d7..cec92d0 100644
--- a/lyt/src/lexer.rs
+++ b/lyt/src/lexer.rs
@@ -29,6 +29,8 @@ pub enum Source {
     Unknown,
 
     File(Arc<Box<Path>>),
+
+    Repl(usize),
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -166,16 +168,12 @@ impl<'a> Lexer<'a> {
             }
         }
 
-        dbg!(&self.collected);
         Ok(self.produce(BareToken::Integer(
             self.collected
                 .iter()
                 .collect::<String>()
                 .parse()
-                .map_err(|e: ParseIntError| {
-                    dbg!(&e);
-                    self.produce_error(e.into())
-                })?,
+                .map_err(|e: ParseIntError| self.produce_error(e.into()))?,
         )))
     }
 }
@@ -188,6 +186,7 @@ impl<'a> Iterator for Lexer<'a> {
             return None;
         }
         if self.done && !self.sent_eof {
+            self.sent_eof = true;
             return Some(Ok(Token {
                 location: None,
                 token: BareToken::EndOfFile,
@@ -309,9 +308,10 @@ mod test {
                 t(pos(1), BareToken::Integer(3)),
                 t(pos(3), BareToken::Plus),
                 t(pos(5), BareToken::Integer(9)),
+                t(Option::None, BareToken::EndOfFile),
             ]),
         );
-        assert_eq!(tokens?.len(), 3);
+        assert_eq!(tokens?.len(), 4);
         Ok(())
     }
 }
diff --git a/lyt/src/parser.rs b/lyt/src/parser.rs
index a0f7fe5..ffe1b82 100644
--- a/lyt/src/parser.rs
+++ b/lyt/src/parser.rs
@@ -2,7 +2,7 @@ use std::{iter::Peekable, vec::IntoIter};
 
 use crate::{ast::*, lexer};
 
-struct Parser {
+pub struct Parser {
     num_tokens_parsed: usize,
 }