diff --git a/src/main.rs b/src/main.rs
index 83c05af..e58f95c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -26,7 +26,10 @@ struct Opt {
 
 fn main() {
     let opt = Opt::from_args();
-    let mut infile = File::open(opt.input).expect("could not open file");
+    // let mut infile = File::open(opt.input).expect("could not open file");
+    let packages = package::PackageRegistry::new();
+    let mut infile = packages.get("builtins").expect("no package").open().expect("could not open file");
+
     let mut input = String::new();
     infile
         .read_to_string(&mut input)
diff --git a/src/package.rs b/src/package.rs
index 6d9e840..ad4a1d0 100644
--- a/src/package.rs
+++ b/src/package.rs
@@ -1,17 +1,25 @@
 use std::collections::BTreeMap;
 use std::path::PathBuf;
+use std::fs::File;
 
-struct Package {
+pub struct Package {
     name: String,
     path: PathBuf,
 }
 
-struct PackageRegistry {
+impl Package {
+    pub fn open(&self) -> Result<File, std::io::Error> {
+        let filepath = self.path.with_file_name("main.hyd");
+        File::open(filepath)
+    }
+}
+
+pub struct PackageRegistry {
     packages: BTreeMap<String, Package>
 }
 
 impl PackageRegistry {
-    fn new() -> Self {
+    pub fn new() -> Self {
         let mut packages = BTreeMap::new();
         packages.insert("builtins".to_string(), Package {
             name: "builtins".to_string(),
@@ -19,4 +27,8 @@ impl PackageRegistry {
         });
         Self { packages }
     }
+
+    pub fn get(&self, name: &str) -> Option<&Package> {
+        self.packages.get(name)
+    }
 }