diff --git a/Cargo.lock b/Cargo.lock
index aeb50eb..9ff7ee4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8,12 +8,82 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "cc"
+version = "1.0.79"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "50d30906286121d95be3d479533b458f87493b30a4b5f79a607db8f5d11aa91f"
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "clap"
+version = "4.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3d7ae14b20b94cb02149ed21a86c423859cbe18dc7ed69845cace50e52b40a5"
+dependencies = [
+ "bitflags",
+ "clap_derive",
+ "clap_lex",
+ "is-terminal",
+ "once_cell",
+ "strsim",
+ "termcolor",
+]
+
+[[package]]
+name = "clap_derive"
+version = "4.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44bec8e5c9d09e439c4335b1af0abaab56dcf3b94999a936e1bb47b9134288f0"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "clap_lex"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "350b9cf31731f9957399229e9b2adc51eeabdfbe9d71d9a0552275fd12710d09"
+dependencies = [
+ "os_str_bytes",
+]
+
+[[package]]
+name = "errno"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f639046355ee4f37944e44f60642c6f3a7efa3cf6b78c78a0d989a8ce6c396a1"
+dependencies = [
+ "errno-dragonfly",
+ "libc",
+ "winapi",
+]
+
+[[package]]
+name = "errno-dragonfly"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa68f1b12764fab894d2755d2518754e71b4fd80ecfb822714a1206c2aab39bf"
+dependencies = [
+ "cc",
+ "libc",
+]
+
 [[package]]
 name = "futures"
 version = "0.3.26"
@@ -109,6 +179,52 @@ dependencies = [
  "slab",
 ]
 
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
+[[package]]
+name = "hermit-abi"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fed44880c466736ef9a5c5b5facefb5ed0785676d0c02d612db14e54f0d84286"
+
+[[package]]
+name = "io-lifetimes"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1abeb7a0dd0f8181267ff8adc397075586500b81b28a73e8a0208b00fc170fb3"
+dependencies = [
+ "libc",
+ "windows-sys",
+]
+
+[[package]]
+name = "is-terminal"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21b6b32576413a8e69b90e952e4a026476040d81017b80445deda5f2d3921857"
+dependencies = [
+ "hermit-abi",
+ "io-lifetimes",
+ "rustix",
+ "windows-sys",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.139"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "201de327520df007757c1f0adce6e827fe8562fbc28bfd9c15571c66ca1f5f79"
+
+[[package]]
+name = "linux-raw-sys"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f051f77a7c8e6957c0696eac88f26b0117e54f52d3fc682ab19397a8812846a4"
+
 [[package]]
 name = "memchr"
 version = "2.5.0"
@@ -119,9 +235,22 @@ checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 name = "moose"
 version = "0.1.0"
 dependencies = [
+ "clap",
  "rstest",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.17.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7e5500299e16ebb147ae15a00a942af264cf3688f47923b8fc2cd5858f23ad3"
+
+[[package]]
+name = "os_str_bytes"
+version = "6.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b7820b9daea5457c9f21c69448905d723fbd21136ccf521748f23fd49e723ee"
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.9"
@@ -134,6 +263,30 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.51"
@@ -187,6 +340,20 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "0.36.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f43abb88211988493c1abb44a70efa56ff0ce98f233b7b276146f1f3f7ba9644"
+dependencies = [
+ "bitflags",
+ "errno",
+ "io-lifetimes",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys",
+]
+
 [[package]]
 name = "semver"
 version = "1.0.16"
@@ -202,6 +369,12 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
+
 [[package]]
 name = "syn"
 version = "1.0.109"
@@ -213,8 +386,120 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be55cf8942feac5c765c2c993422806843c9a9a45d4d5c407ad6dd2ea95eb9b6"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "84a22b9f218b40614adcb3f4ff08b703773ad44fa9423e4e0d346d5db86e4ebc"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
+[[package]]
+name = "windows-sys"
+version = "0.45.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75283be5efb2831d37ea142365f009c02ec203cd29a3ebecbc093d52315b66d0"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e2522491fbfcd58cc84d47aeb2958948c4b8982e9a2d8a2a35bbaed431390e7"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c9864e83243fdec7fc9c5444389dcbbfd258f745e7853198f365e3c4968a608"
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c8b1b673ffc16c47a9ff48570a9d85e25d265735c503681332589af6253c6c7"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "de3887528ad530ba7bdbb1faa8275ec7a1155a45ffa57c37993960277145d640"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf4d1122317eddd6ff351aa852118a2418ad4214e6613a50e0191f7004372605"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1040f221285e17ebccbc2591ffdc2d44ee1f9186324dd3e84e99ac68d699c45"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "628bfdf232daa22b0d64fdb62b09fcc36bb01f05a3939e20ab73aaf9470d0463"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "447660ad36a13288b1db4d4248e857b510e8c3a225c822ba4fb748c0aafecffd"
diff --git a/Cargo.toml b/Cargo.toml
index 92799fc..b5d2c76 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,9 +1,12 @@
 [package]
 name = "moose"
 version = "0.1.0"
+authors =["Devon Tingley <dtingley@twilit.io>"]
+description = "Oxidized interpretor for the monkey programming language"
 edition = "2021"
 
 [dependencies]
+clap = { version = "4.1.8", features = ["derive"] }
 
 [dev-dependencies]
 rstest = "0.16.0"
diff --git a/examples/basic.ms b/examples/basic.ms
new file mode 100644
index 0000000..a36f43e
--- /dev/null
+++ b/examples/basic.ms
@@ -0,0 +1,7 @@
+print(5 + 5);
+
+if (5 == 5) {
+    print(true);
+} else {
+    print(false);
+}
diff --git a/src/lexer/mod.rs b/src/lexer/mod.rs
index 2bbea07..5794c50 100644
--- a/src/lexer/mod.rs
+++ b/src/lexer/mod.rs
@@ -17,8 +17,30 @@ pub fn tokenize(input: &str) -> Vec<Token> {
 
 fn next_token(input: &mut Peekable<Chars>) -> Option<Token> {
     let tok = match input.next()? {
-        '=' => Token::Assign,
         '+' => Token::Plus,
+        '-' => Token::Minus,
+        '*' => Token::Asterisk,
+        '/' => Token::ForwardSlash,
+
+        '!' => {
+            if input.peek() == Some(&'=') {
+                input.next();
+                Token::NotEqual
+            } else {
+                Token::Bang
+            }
+        }
+        '=' => {
+            if input.peek() == Some(&'=') {
+                input.next();
+                Token::Equal
+            } else {
+                Token::Assign
+            }
+        }
+
+        '<' => Token::LessThan,
+        '>' => Token::GreaterThan,
 
         ',' => Token::Comma,
         ';' => Token::Semicolon,
@@ -56,8 +78,13 @@ fn read_ident(input: &mut Peekable<Chars>, first: char) -> Token {
     // Check if our ident is a keyword
     let ident = toks.iter().cloned().collect::<String>();
     match ident.as_str() {
+        "true" => Token::True,
+        "false" => Token::False,
         "fn" => Token::Function,
         "let" => Token::Let,
+        "if" => Token::If,
+        "else" => Token::Else,
+        "return" => Token::Return,
 
         ident => Token::Ident(ident.to_owned()),
     }
@@ -102,16 +129,68 @@ mod tests {
             Token::Semicolon,
         ])]
     #[case(
-        "
-    let five = 5;
-    let ten = 10;
+        "!-/*5; 5 < 10 > 5;",
+        vec![
+            Token::Bang,
+            Token::Minus,
+            Token::ForwardSlash,
+            Token::Asterisk,
+            Token::Int(5),
+            Token::Semicolon,
+            Token::Int(5),
+            Token::LessThan,
+            Token::Int(10),
+            Token::GreaterThan,
+            Token::Int(5),
+            Token::Semicolon,
+        ])]
+    #[case(
+        "5 != 6",
+        vec![
+            Token::Int(5),
+            Token::NotEqual,
+            Token::Int(6),
+    ])]
+    #[case(
+        "8 == 8",
+        vec![
+            Token::Int(8),
+            Token::Equal,
+            Token::Int(8),
+    ])]
+    #[case(
+        "if (5 < 7) {
+            return true
+        } else {
+            return false
+        }",
+        vec![
+            Token::If,
+            Token::LeftParenthesis,
+            Token::Int(5),
+            Token::LessThan,
+            Token::Int(7),
+            Token::RightParenthesis,
+            Token::LeftBrace,
+            Token::Return,
+            Token::True,
+            Token::RightBrace,
+            Token::Else,
+            Token::LeftBrace,
+            Token::Return,
+            Token::False,
+            Token::RightBrace
+        ])]
+    #[case(
+        "let five = 5;
+        let ten = 10;
 
-    let add = fn(x, y) {
-        x + y;
-    }
+        let add = fn(x, y) {
+            x + y;
+        }
 
-    let result = add(five, ten);
-    ",
+        let result = add(five, ten);
+        ",
         vec![
             Token::Let,
             Token::Ident("five".into()),
diff --git a/src/lexer/tokens.rs b/src/lexer/tokens.rs
index 0532bfd..d426e22 100644
--- a/src/lexer/tokens.rs
+++ b/src/lexer/tokens.rs
@@ -7,8 +7,18 @@ pub enum Token {
     Int(i64),
 
     // Operators
+    Bang,
+
     Assign,
     Plus,
+    Minus,
+    Asterisk,
+    ForwardSlash,
+
+    Equal,
+    NotEqual,
+    LessThan,
+    GreaterThan,
 
     // Delimiters
     Comma,
@@ -20,6 +30,12 @@ pub enum Token {
     RightBrace,
 
     // Keywords
+    True,
+    False,
+
     Function,
     Let,
+    If,
+    Else,
+    Return,
 }
diff --git a/src/main.rs b/src/main.rs
index 077d2fa..942d417 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,43 @@
+use std::fs;
+use std::io::{self, Write};
+
+use clap::{CommandFactory, Parser};
+
 mod lexer;
 
-fn main() {
-    println!("{:?}", lexer::tokenize("asdf"));
+#[derive(Parser)]
+#[command(author, version, about)]
+struct Args {
+    path: Option<String>,
+}
+
+fn main() {
+    let args = Args::parse();
+    let cmd = Args::command();
+
+    match args.path {
+        Some(path) => {
+            let input = fs::read_to_string(&path).unwrap();
+            let tokens = lexer::tokenize(&input);
+            println!("{:?}", tokens);
+        }
+
+        None => start_repl(cmd.get_version().unwrap()),
+    }
+}
+
+fn start_repl(version: &str) {
+    println!("Moose {} REPL", version);
+    let mut input = String::new();
+    loop {
+        print!("> ");
+        io::stdout().flush().expect("failed to write to stdout");
+
+        io::stdin()
+            .read_line(&mut input)
+            .expect("failed to read from stdin");
+
+        let tokens = lexer::tokenize(&input);
+        println!("{:?}", tokens);
+    }
 }