diff --git a/ToDo.md b/ToDo.md
index 66a6be7..0b6b56d 100644
--- a/ToDo.md
+++ b/ToDo.md
@@ -9,4 +9,4 @@
 * recursive compiling
 * concurrent compiling
 * inline buildin function call -> foo(a)(bar(x)(y));
-* negative values e.g. -1, operator !
+* ~~negative values e.g. -1, operator !~~
diff --git a/in/complex.asl b/in/complex.asl
index b3140cc..6d38b29 100644
--- a/in/complex.asl
+++ b/in/complex.asl
@@ -1,13 +1 @@
-diag_log()("easyHC: started");
-publicVariable()("easyHCpresent");
-
-if isNil()("easyHCpresent") {
-    easyHCpresent = 1; // HC client ID
-}
-
-if isServer()() && hasInterface()() {
-    easyHCpresent = owner()(player);
-    //diag_log()(format()("easyHC: found headless client with ID %1.", easyHCpresent));
-}
-
-// ...
+foo(player)("head");
diff --git a/src/asl/parser.go b/src/asl/parser.go
index a334e96..25a5555 100644
--- a/src/asl/parser.go
+++ b/src/asl/parser.go
@@ -379,10 +379,20 @@ func parseExpression(out bool) string {
 func parseIdentifier() string {
     output := ""
     
-    if seek("(") {
+    if seek("(") && !accept("!") && !accept("-") {
         name := get().token
         next()
         output = "("+parseFunctionCall(false, name)+")"
+    } else if accept("!") || accept("-") {
+        output = get().token
+        next()
+        
+        if !accept("(") {
+            output += get().token
+            next()
+        } else {
+            output += parseTerm()
+        }
     } else {
         output = get().token
         next()
diff --git a/src/asl/parser_test.go b/src/asl/parser_test.go
index e97f241..95e9894 100644
--- a/src/asl/parser_test.go
+++ b/src/asl/parser_test.go
@@ -68,7 +68,7 @@ func TestParserAssignResult(t *testing.T) {
 
 func TestParserExpression(t *testing.T) {
     got := getCompiled(t, "test/parser_expression.asl")
-    want := "x = (1+(2+3))/(6*(someVariable+99-100))-(20)+anotherVariable+([] call foo);\n"
+    want := "x = -(1+(2+3))/(6*(someVariable+99-100))-(20)+!anotherVariable+([] call foo);\n"
     
     equal(t, got, want)
 }
diff --git a/test/parser_expression.asl b/test/parser_expression.asl
index fc5b371..d56f5c2 100644
--- a/test/parser_expression.asl
+++ b/test/parser_expression.asl
@@ -1 +1 @@
-var x = (1+(2+3))/(6*(someVariable+99-100))-(20)+anotherVariable+foo();
+var x = -(1+(2+3))/(6*(someVariable+99-100))-(20)+!anotherVariable+foo();