diff --git a/Makefile b/Makefile
index dbfb297a..ee29731b 100644
--- a/Makefile
+++ b/Makefile
@@ -47,3 +47,10 @@ install:
 	# Install systemd user service
 	mkdir -p $(DESTDIR)$(PREFIX)/lib/systemd/user
 	install -m 644 aw-server.service $(DESTDIR)$(PREFIX)/lib/systemd/user/aw-server.service
+
+coverage:
+	export CARGO_INCREMENTAL=0
+	export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
+	export RUSTDOCFLAGS="-Cpanic=abort"
+	cargo build --verbose $(cargoflag)
+	cargo test --verbose $(cargoflag)
diff --git a/aw-query/benches/benchmark.rs b/aw-query/benches/benchmark.rs
index b1971044..440db3ab 100644
--- a/aw-query/benches/benchmark.rs
+++ b/aw-query/benches/benchmark.rs
@@ -70,7 +70,7 @@ mod query_benchmarks {
         }
         //
         let mut event_list = Vec::new();
-        for i in 0..3000 {
+        for i in 0..30000 {
             let e = Event {
                 id: None,
                 timestamp: chrono::Utc::now() + Duration::seconds(i),
diff --git a/aw-query/src/ast.rs b/aw-query/src/ast.rs
index bba16557..0d9526bc 100644
--- a/aw-query/src/ast.rs
+++ b/aw-query/src/ast.rs
@@ -24,6 +24,7 @@ pub enum Expr_ {
     Equal(Box<Expr>, Box<Expr>),
 
     Var(String),
+    VarRef(String),
     Assign(String, Box<Expr>),
     Function(String, Box<Expr>),
     If(Vec<(Box<Expr>, Vec<Expr>)>),
diff --git a/aw-query/src/interpret.rs b/aw-query/src/interpret.rs
index 48ba212c..ccf41121 100644
--- a/aw-query/src/interpret.rs
+++ b/aw-query/src/interpret.rs
@@ -182,11 +182,17 @@ fn interpret_expr(
             env.insert(var, val);
             Ok(DataType::None())
         }
-        // FIXME: avoid clone, it's slow
-        Var(var) => match env.get(&var) {
-            Some(v) => Ok(v.clone()),
+        Var(var) => match env.remove(&var) {
+            Some(v) => Ok(v),
             None => Err(QueryError::VariableNotDefined(var.to_string())),
         },
+        VarRef(var) => {
+            // TODO: Remove clone
+            match env.get(&var) {
+                Some(v) => Ok(v.clone()),
+                None => Err(QueryError::VariableNotDefined(var.to_string())),
+            }
+        }
         Bool(lit) => Ok(DataType::Bool(lit)),
         Number(lit) => Ok(DataType::Number(lit)),
         String(litstr) => Ok(DataType::String(litstr.to_string())),
diff --git a/aw-query/src/lexer.rs b/aw-query/src/lexer.rs
index 1701790e..02cbac52 100644
--- a/aw-query/src/lexer.rs
+++ b/aw-query/src/lexer.rs
@@ -13,6 +13,7 @@ pub enum Token {
     Number(f64),
     String(String),
     Plus,
+    Ampersand,
     Minus,
     Star,
     Slash,
@@ -69,6 +70,7 @@ lexer! {
 
     r#"=="# => (Token::Equals, text),
     r#"="# => (Token::Assign, text),
+    r#"\&"# => (Token::Ampersand, text),
     r#"\+"# => (Token::Plus, text),
     r#"-"# => (Token::Minus, text),
     r#"\*"# => (Token::Star, text),
diff --git a/aw-query/src/parser.rs b/aw-query/src/parser.rs
index b7541a1c..b64ebb26 100644
--- a/aw-query/src/parser.rs
+++ b/aw-query/src/parser.rs
@@ -246,6 +246,10 @@ parser! {
             span: span!(),
             node: Expr_::Var(v),
         },
+        Ampersand Ident(v) => Expr {
+            span: span!(),
+            node: Expr_::VarRef(v),
+        },
         Bool(b) => Expr {
             span: span!(),
             node: Expr_::Bool(b),
diff --git a/aw-query/tests/query.rs b/aw-query/tests/query.rs
index 1ecac21b..71f91381 100644
--- a/aw-query/tests/query.rs
+++ b/aw-query/tests/query.rs
@@ -232,7 +232,7 @@ mod query_tests {
         let code = String::from(
             "
             a=True; n=1;
-            if a { n=2; }
+            if &a { n=2; }
             return n;",
         );
         match aw_query::query(&code, &interval, &ds).unwrap() {
@@ -269,8 +269,8 @@ mod query_tests {
         let code = String::from(
             "
             a=False; b=True; n=1;
-            if a { n=2; }
-            elif b { n=3; }
+            if &a { n=2; }
+            elif &b { n=3; }
             return n;",
         );
         match aw_query::query(&code, &interval, &ds).unwrap() {
@@ -282,8 +282,8 @@ mod query_tests {
         let code = String::from(
             "
             a=False; b=True; n=1;
-            if a { n=2; }
-            elif a { n=3; }
+            if &a { n=2; }
+            elif &a { n=3; }
             else { n=4; }
             return n;",
         );
@@ -296,7 +296,7 @@ mod query_tests {
         let code = String::from(
             "
             a=True; n=1;
-            if a { if a { n = 2; } }
+            if &a { if &a { n = 2; } }
             return n;",
         );
         match aw_query::query(&code, &interval, &ds).unwrap() {
@@ -359,16 +359,16 @@ mod query_tests {
             events = concat(events, query_bucket("{}"));
             events = categorize(events, [[["test"], {{ "type": "regex", "regex": "value$" }}], [["test", "testing"], {{ "type": "regex", "regex": "value$" }}]]);
             events = tag(events, [["testtag", {{ "type": "regex", "regex": "test$" }}], ["another testtag", {{ "type": "regex", "regex": "test-pat$" }}]]);
-            total_duration = sum_durations(events);
+            total_duration = sum_durations(&events);
             bucketnames = query_bucket_names();
             print("test", "test2");
-            url_events = split_url_events (events);
-            filtered_events = filter_period_intersect(events, events);
-            filtered_events = filter_keyvals(events, "$category", [["Uncategorized"]]);
-            filtered_events = filter_keyvals_regex(events, "key", "regex");
-            chunked_events = chunk_events_by_key(events, "key");
-            merged_events = merge_events_by_keys(events, ["key"]);
-            return  merged_events;"#,
+            events = split_url_events (events);
+            events = filter_period_intersect(&events, &events);
+            events = filter_keyvals(events, "$category", [["Uncategorized"]]);
+            events = filter_keyvals_regex(events, "key", "regex");
+            events = chunk_events_by_key(events, "key");
+            events = merge_events_by_keys(events, ["key"]);
+            return events;"#,
             "testid", "testid"
         );
         match aw_query::query(&code, &interval, &ds).unwrap() {
diff --git a/aw-webui b/aw-webui
index 1a969b3e..9247aedb 160000
--- a/aw-webui
+++ b/aw-webui
@@ -1 +1 @@
-Subproject commit 1a969b3e3bdec7ee5338a3e54238370cbdd9be97
+Subproject commit 9247aedb2a62ee1dd84c812ba5de04f400fdcbf2