diff --git a/lib/src/environment.dart b/lib/src/environment.dart
index 9088f336..c10c591b 100644
--- a/lib/src/environment.dart
+++ b/lib/src/environment.dart
@@ -3,12 +3,13 @@
 // https://opensource.org/licenses/MIT.
 
 import 'value.dart';
+import 'utils.dart';
 
 class Environment {
   /// Base is global scope.
-  final _variables = [<String, Value>{}];
+  final _variables = [separatorIndependentMap/*<Value>*/()];
 
-  final _variableIndices = <String, int>{};
+  final _variableIndices = separatorIndependentMap/*<int>*/();
 
   Value getVariable(String name) =>
       _variables[_variableIndices[name] ?? 0][name];
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 4eb8ad0e..d140bf5b 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -58,13 +58,49 @@ String unvendor(String name) {
   return name;
 }
 
+bool equalsIgnoreSeparator(String string1, String string2) {
+  print("eis: $string1 $string2");
+  if (identical(string1, string2)) return true;
+  if (string1 == null || string2 == null) return false;
+  if (string1.length != string2.length) return false;
+  for (var i = 0; i < string1.length; i++) {
+    var codeUnit1 = string1.codeUnitAt(i);
+    var codeUnit2 = string2.codeUnitAt(i);
+    if (codeUnit1 == codeUnit2) continue;
+    if (codeUnit1 == $dash) {
+      if (codeUnit2 != $underscore) return false;
+    } else if (codeUnit1 == $underscore) {
+      if (codeUnit2 != $dash) return false;
+    } else {
+      return false;
+    }
+  }
+  return true;
+}
+
+int hashCodeIgnoreSeparator(String string) {
+  var hash = 4603;
+  for (var i = 0; i < string.length; i++) {
+    var codeUnit = string.codeUnitAt(i);
+    if (codeUnit == $underscore) codeUnit = $dash;
+    hash &= 0x3FFFFFF;
+    hash *= 33;
+    hash ^= codeUnit;
+  }
+  return hash;
+}
+
 bool equalsIgnoreCase(String string1, String string2) {
-  if (string1 == null) return string2 == null;
-  if (string2 == null) return false;
+  if (identical(string1, string2)) return true;
+  if (string1 == null || string2 == null) return false;
   if (string1.length != string2.length) return false;
   return string1.toUpperCase() == string2.toUpperCase();
 }
 
+Map/*<V>*/ separatorIndependentMap/*<V>*/() =>
+    new LinkedHashMap(
+        equals: equalsIgnoreSeparator, hashCode: hashCodeIgnoreSeparator);
+
 bool almostEquals(num number1, num number2) =>
     (number1 - number2).abs() < _epsilon;