diff --git a/Slang/slang.html b/Slang/slang.html
index e26b9f9..ce530bb 100755
--- a/Slang/slang.html
+++ b/Slang/slang.html
@@ -59,6 +59,11 @@
 	font-family: monospace;
 }
 
+.word[builtin=yes] {
+	font-style: italic;
+	color: blue;
+}
+
 #stack {
 	opacity: 0.8;
 }
@@ -69,6 +74,9 @@
 <script>
 
 function stringifySlangCode(code){
+	if(code == null){
+		return code
+	}
 	if(typeof(code) == typeof('str') && /\s/.test(code)){
 		return '\''+code+'\''
 	} else if(code.constructor.name == 'Array'){
@@ -163,10 +171,13 @@ function showAvailableWords(){
 		})
 		.map(function(e){
 			var code = NAMESPACE[e]
+			var builtin = 'no'
 			if(code.constructor.name == 'Array'){
 				code = stringifySlangCode(code)
+			} else if(typeof(code) == typeof(function(){})){
+				builtin = 'yes'
 			}
-			return '<span title="'+code+'">'+e+'</span>'
+			return '<span class="word" builtin="'+builtin+'" title="'+code+'">'+e+'</span>'
 		})
 		.join(', ')
 }
diff --git a/Slang/slang.js b/Slang/slang.js
index 74137d5..a44b297 100755
--- a/Slang/slang.js
+++ b/Slang/slang.js
@@ -151,6 +151,7 @@ var NAMESPACE = {
 	// ... [ ... ] -- ... ...
 	'b2s': function(context){
 		var c = context.stack.pop()
+		c = c === undefined ? [] : c
 		context.stack.splice.apply(context.stack, [context.stack.length, 0].concat(c))
 	},
 	'print': function(context){
@@ -294,6 +295,11 @@ var NAMESPACE = {
 	'dup': function(context){
 		return context.stack[context.stack.length-1]
 	},
+	// x -- x'
+	// NOTE: this will do a deep copy...
+	'clone': function(context){
+		return JSON.parse(JSON.stringify(context.stack.pop()))
+	},
 	// x --
 	'drop': function(context){
 		context.stack.pop()
@@ -497,6 +503,9 @@ var BOOTSTRAP = [
 '--',
 '-- With that out of the way, let\'s start with the bootstrap...',
 '--',
+'-- make a new block instance shorthand...',
+':: [] [ [ ] clone ]',
+'',
 ':: _swap ( x | y -- y | x ) [ 1 1 _swapN ]',
 ':: _push ( x |  -- | x ) [ 0 _swapN ]',
 ':: _pull (  | x -- x |  ) [ 0 swap _swapN ]',