diff --git a/Cargo.lock b/Cargo.lock
index 1583cfcf..0839789f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,237 @@
 # It is not intended for manual editing.
 version = 3
 
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+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
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+
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+checksum = "535434c063ced786eb04aaf529308092c5ab60889e8fe24275d15de07b01fa97"
+dependencies = [
+ "atty",
+ "bitflags",
+ "clap_derive",
+ "clap_lex",
+ "indexmap",
+ "lazy_static",
+ "strsim",
+ "termcolor",
+ "textwrap",
+]
+
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+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
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+ "os_str_bytes",
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+ "libc",
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 [[package]]
 name = "neptune"
 version = "0.1.0"
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diff --git a/Cargo.toml b/Cargo.toml
index 04826e3d..56a6eb4f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+clap = { version = "3.1.14", features = ["derive"] }
diff --git a/example/plutus-core b/example/plutus-core
new file mode 100644
index 00000000..e91bf68f
--- /dev/null
+++ b/example/plutus-core
@@ -0,0 +1,3 @@
+(program 1.0.0
+    [[(builtin addInteger) (con integer 4)] (con integer 8)]
+)
\ No newline at end of file
diff --git a/src/ast.rs b/src/ast.rs
new file mode 100644
index 00000000..9911163f
--- /dev/null
+++ b/src/ast.rs
@@ -0,0 +1,45 @@
+pub struct Program<'a> {
+    pub version: String,
+    pub term: &'a Term<'a>,
+}
+
+pub enum Term<'a> {
+    // tag: 0
+    Var(String),
+    // tag: 1
+    Delay(&'a Term<'a>),
+    // tag: 2
+    Lambda {
+        parameter_name: String,
+        body: &'a Term<'a>,
+    },
+    // tag: 3
+    Apply {
+        function: &'a Term<'a>,
+        argument: &'a Term<'a>,
+    },
+    // tag: 4
+    Constant(Constant),
+    // tag: 5
+    Force(&'a Term<'a>),
+    // tag: 6
+    Error(&'a Term<'a>),
+    // tag: 7
+    // Builtin
+}
+
+pub enum Constant {
+    // TODO: figure out the right size for this
+    // tag: 0
+    Integer(i64),
+    // tag: 1
+    ByteString(Vec<u8>),
+    // tag: 2
+    String(String),
+    // tag: 3
+    Char(char),
+    // tag: 4
+    Unit,
+    // tag: 5
+    Bool(bool),
+}
diff --git a/src/cli.rs b/src/cli.rs
new file mode 100644
index 00000000..e7a6534f
--- /dev/null
+++ b/src/cli.rs
@@ -0,0 +1,14 @@
+use std::path::PathBuf;
+
+use clap::Parser;
+
+#[derive(Parser)]
+pub struct Cli {
+    pub input: PathBuf,
+}
+
+impl Default for Cli {
+    fn default() -> Self {
+        Self::parse()
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 00000000..edde5527
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,2 @@
+pub mod ast;
+pub mod cli;
diff --git a/src/main.rs b/src/main.rs
index e7a11a96..49a63cc4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,7 @@
+use neptune::cli::Cli;
+
 fn main() {
-    println!("Hello, world!");
+    let args = Cli::default();
+
+    println!("loading {}", args.input.display());
 }