diff --git a/Cargo.lock b/Cargo.lock
index 93c2900..ad13ad1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -16,6 +16,7 @@ dependencies = [
  "codepage-437",
  "insta",
  "nom",
+ "peg_macro",
  "pest",
 ]
 
@@ -126,6 +127,13 @@ version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
+[[package]]
+name = "peg_macro"
+version = "0.1.0"
+dependencies = [
+ "quote",
+]
+
 [[package]]
 name = "pest"
 version = "2.8.0"
diff --git a/Cargo.toml b/Cargo.toml
index ca7c051..0628280 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2024"
 [dependencies]
 anyhow = "1.0.86"
 codepage-437 = "0.1.0"
+peg_macro = { path = "./peg_macro"}
 insta = "1.39.0"
 nom = "7.1.3"
 pest = "2.7.15"
@@ -22,3 +23,6 @@ similar.opt-level = 3
 [[bin]]
 name = "zasm"
 path = "src/main.rs"
+
+[workspace]
+members = [".", "peg_macro"]
diff --git a/peg_macro/.gitignore b/peg_macro/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/peg_macro/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/peg_macro/Cargo.toml b/peg_macro/Cargo.toml
new file mode 100644
index 0000000..5307907
--- /dev/null
+++ b/peg_macro/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "peg_macro"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+quote = "1.0.40"
diff --git a/peg_macro/src/lib.rs b/peg_macro/src/lib.rs
new file mode 100644
index 0000000..548de23
--- /dev/null
+++ b/peg_macro/src/lib.rs
@@ -0,0 +1,27 @@
+use proc_macro::TokenStream;
+use quote::quote;
+
+#[proc_macro]
+pub fn grammar(ts: TokenStream) -> TokenStream {
+    let token = ts.into_iter().next().expect("must have at least one token");
+    let result = match token {
+        proc_macro::TokenTree::Literal(literal) => {
+            let s = literal.to_string();
+            let c = s.chars().next().unwrap_or('\0');
+            match c {
+                '0'..'9' => {
+                    let val: usize = s.parse().unwrap();
+                    quote! { Some(crate::peg::Foo::Bar(#val)) }
+                }
+                '"' => {
+                    let inner = &s[1..s.len() - 1];
+                    quote! { Some(crate::peg::Foo::Baz(#inner.into())) }
+                }
+                _ => quote! { None },
+            }
+        }
+        _ => quote! { None },
+    };
+
+    quote! { println!("Hello, world! {:?}", #result); }.into()
+}
diff --git a/src/main.rs b/src/main.rs
index aae65d2..2f9c7f3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,15 +1,20 @@
 mod encoding;
 mod labels;
+mod peg;
 mod preprocess;
 mod world;
 
 use anyhow::anyhow;
 use labels::labels::print_labels;
+use peg_macro::grammar;
 use preprocess::eval::Context;
 use std::{env, error::Error, fs, path::PathBuf, process::exit};
 use world::World;
 
 fn main() -> Result<(), Box<dyn Error>> {
+    grammar!(123);
+    grammar!("abc");
+
     let args: Vec<String> = env::args().collect();
     if args.len() != 2 {
         eprintln!("Usage: {} WORLD_FILE", args[0]);
diff --git a/src/peg/mod.rs b/src/peg/mod.rs
new file mode 100644
index 0000000..ad85da9
--- /dev/null
+++ b/src/peg/mod.rs
@@ -0,0 +1,3 @@
+pub mod peg;
+
+pub use peg::*;
diff --git a/src/peg/peg.rs b/src/peg/peg.rs
new file mode 100644
index 0000000..e081159
--- /dev/null
+++ b/src/peg/peg.rs
@@ -0,0 +1,6 @@
+#[derive(Debug)]
+#[allow(dead_code)]
+pub enum Foo {
+    Bar(usize),
+    Baz(String),
+}