diff --git a/Cargo.toml b/Cargo.toml
index e60dbc6..83c3fe6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,4 +11,9 @@ regex = "1.0.5"
 unicase = "2.2.0"
 
 [dev-dependencies]
+criterion = "0.2.0"
 tempfile = "3.0.0"
+
+[[bench]]
+name = "eval"
+harness = false
diff --git a/benches/eval.rs b/benches/eval.rs
new file mode 100644
index 0000000..8071f51
--- /dev/null
+++ b/benches/eval.rs
@@ -0,0 +1,136 @@
+#[macro_use]
+extern crate criterion;
+extern crate loot_condition_interpreter;
+
+use criterion::Criterion;
+use loot_condition_interpreter::{Expression, GameType, State};
+
+fn generate_active_plugins() -> Vec<String> {
+    let mut vec: Vec<String> = (0..255).map(|i| format!("Blank{}.esm", i)).collect();
+    vec.push("Blank.esm".into());
+    vec
+}
+
+fn generate_plugin_versions() -> Vec<(String, String)> {
+    let mut vec: Vec<(String, String)> = (0..255)
+        .map(|i| (format!("Blank{}.esm", i), "5".to_string()))
+        .collect();
+    vec.push(("Blank.esm".into(), "5".into()));
+    vec
+}
+
+fn criterion_benchmark(c: &mut Criterion) {
+    c.bench_function("Expression.eval() file(path)", |b| {
+        let state = State::new(GameType::Tes4, ".".into(), ".".into());
+        let expression = Expression::parse("file(\"Cargo.toml\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() file(regex)", |b| {
+        let state = State::new(GameType::Tes4, ".".into(), ".".into());
+        let expression = Expression::parse("file(\"Cargo.*\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() active(path)", |b| {
+        let state = State::new(
+            GameType::Tes4,
+            "testing-plugins/Oblivion/Data".into(),
+            ".".into(),
+        ).with_active_plugins(&generate_active_plugins());
+
+        let expression = Expression::parse("active(\"Blank.esm\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() active(regex)", |b| {
+        let state = State::new(
+            GameType::Tes4,
+            "testing-plugins/Oblivion/Data".into(),
+            ".".into(),
+        ).with_active_plugins(&generate_active_plugins());
+
+        let expression = Expression::parse("active(\"Blank.*\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() many()", |b| {
+        let state = State::new(GameType::Tes4, ".".into(), ".".into());
+        let expression = Expression::parse("many(\"Cargo.*\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() many_active()", |b| {
+        let state = State::new(
+            GameType::Tes4,
+            "testing-plugins/Oblivion/Data".into(),
+            ".".into(),
+        ).with_active_plugins(&generate_active_plugins());
+
+        let expression = Expression::parse("many_active(\"Blank.*\")").unwrap().1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() checksum()", |b| {
+        let state = State::new(
+            GameType::Tes4,
+            "testing-plugins/Oblivion/Data".into(),
+            ".".into(),
+        );
+        let expression = Expression::parse("checksum(\"Blank.esm\", 374E2A6F)")
+            .unwrap()
+            .1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() version(plugin)", |b| {
+        let state = State::new(
+            GameType::Tes4,
+            "testing-plugins/Oblivion/Data".into(),
+            ".".into(),
+        ).with_plugin_versions(&generate_plugin_versions());
+
+        let expression = Expression::parse("version(\"Blank.esm\", \"5.0\", ==)")
+            .unwrap()
+            .1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+
+    c.bench_function("Expression.eval() version(executable)", |b| {
+        let state = State::new(GameType::Tes4, ".".into(), ".".into());
+        let expression = Expression::parse(
+            "version(\"loot_api-0.13.8-0-g47797cc_dev-win32/loot_api.dll\", \"0.13.8.0\", ==)",
+        ).unwrap()
+        .1;
+
+        b.iter(|| {
+            assert!(expression.eval(&state).unwrap());
+        });
+    });
+}
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);
diff --git a/src/lib.rs b/src/lib.rs
index 82edaff..72b465b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,6 +52,7 @@ impl From<pelite::resources::FindError> for Error {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum GameType {
     Tes4,
     Tes5,
@@ -84,6 +85,7 @@ impl GameType {
     }
 }
 
+#[derive(Debug)]
 pub struct State {
     game_type: GameType,
     /// Game Data folder path.
@@ -100,6 +102,39 @@ pub struct State {
     condition_cache: RwLock<HashMap<Function, bool>>,
 }
 
+impl State {
+    pub fn new(game_type: GameType, data_path: PathBuf, loot_path: PathBuf) -> Self {
+        State {
+            game_type,
+            data_path,
+            loot_path,
+            active_plugins: HashSet::default(),
+            crc_cache: RwLock::default(),
+            plugin_versions: HashMap::default(),
+            condition_cache: RwLock::default(),
+        }
+    }
+
+    pub fn with_plugin_versions<T: AsRef<str>, V: ToString>(
+        mut self,
+        plugin_versions: &[(T, V)],
+    ) -> Self {
+        self.plugin_versions = plugin_versions
+            .iter()
+            .map(|(p, v)| (p.as_ref().to_lowercase(), v.to_string()))
+            .collect();
+        self
+    }
+
+    pub fn with_active_plugins<T: AsRef<str>>(mut self, active_plugins: &[T]) -> Self {
+        self.active_plugins = active_plugins
+            .into_iter()
+            .map(|s| s.as_ref().to_lowercase())
+            .collect();
+        self
+    }
+}
+
 /// Compound conditions joined by 'or'
 #[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
 pub struct Expression(Vec<CompoundCondition>);