diff --git a/lib/utils/mu-sexp.cc b/lib/utils/mu-sexp.cc
index a588f7c0..cfc9812e 100644
--- a/lib/utils/mu-sexp.cc
+++ b/lib/utils/mu-sexp.cc
@@ -101,7 +101,7 @@ parse_string(const std::string& expr, size_t& pos)
 	}
 
 	if (escape || expr[pos] != '"')
-		throw parsing_error(pos, "unterminated string '%s'", str.c_str());
+		return Err(parsing_error(pos, "unterminated string '%s'", str.c_str()));
 
 	++pos;
 	return Ok(Sexp{std::move(str)});
@@ -158,10 +158,11 @@ parse(const std::string& expr, size_t& pos)
 		else if (isalpha(kar) || kar == ':')
 			return parse_symbol(expr, pos);
 		else
-			throw parsing_error(pos, "unexpected character '%c", kar);
+			return Err(parsing_error(pos, "unexpected character '%c", kar));
 	});
 
-	pos = skip_whitespace(expr, pos);
+	if (sexp)
+		pos = skip_whitespace(expr, pos);
 
 	return sexp;
 }
@@ -324,6 +325,7 @@ test_list()
 		Sexp s;
 		g_assert_true(s.listp());
 		g_assert_true(s.to_string() == "()");
+		g_assert_true(Sexp::type_name(s.type()) == "list");
 		g_assert_true(s.empty());
 	}
 
@@ -333,11 +335,22 @@ test_list()
 			Sexp(123),
 			Sexp::Symbol("world")
 		};
-		Sexp s{std::move(items)};
+		const Sexp s{std::move(items)};
 		g_assert_false(s.empty());
 		g_assert_cmpuint(s.size(),==,3);
 		g_assert_true(s.to_string() == "(\"hello\" 123 world)");
-		//g_assert_true(s.to_string() == "(\"hello\" 123 world)");
+
+
+		/* copy */
+		Sexp s2 = s;
+		g_assert_true(s2.to_string() == "(\"hello\" 123 world)");
+
+		/* move */
+		Sexp s3 = std::move(s2);
+		g_assert_true(s3.to_string() == "(\"hello\" 123 world)");
+
+		s3.clear();
+		g_assert_true(s3.empty());
 	}
 
 }
@@ -350,6 +363,7 @@ test_string()
 		g_assert_true(s.stringp());
 		g_assert_true(s.string()=="hello");
 		g_assert_true(s.to_string()=="\"hello\"");
+		g_assert_true(Sexp::type_name(s.type()) == "string");
 	}
 
 	{
@@ -368,6 +382,7 @@ test_number()
 		g_assert_true(s.numberp());
 		g_assert_cmpint(s.number(),==,123);
 		g_assert_true(s.to_string() == "123");
+		g_assert_true(Sexp::type_name(s.type()) == "number");
 	}
 
 	{
@@ -386,6 +401,7 @@ test_symbol()
 		g_assert_true(s.symbolp());
 		g_assert_true(s.symbol()=="hello");
 		g_assert_true (s.to_string()=="hello");
+		g_assert_true(Sexp::type_name(s.type()) == "symbol");
 	}
 
 	{
@@ -469,6 +485,19 @@ bar")",
 		    "\"foo\nbar\"");
 }
 
+static void
+test_parser_fail()
+{
+	g_assert_false(!!Sexp::parse("\""));
+	g_assert_false(!!Sexp::parse("123abc"));
+	g_assert_false(!!Sexp::parse("("));
+	g_assert_false(!!Sexp::parse(")"));
+	g_assert_false(!!Sexp::parse("(hello (boo))))"));
+
+	g_assert_true(Sexp::type_name(static_cast<Sexp::Type>(-1)) == "<error>");
+}
+
+
 int
 main(int argc, char* argv[])
 try {
@@ -483,6 +512,8 @@ try {
 	g_test_add_func("/sexp/add-multi",  test_add_multi);
 	g_test_add_func("/sexp/plist",  test_plist);
 	g_test_add_func("/sexp/parser", test_parser);
+	g_test_add_func("/sexp/parser-fail", test_parser_fail);
+
 	return g_test_run();
 
 } catch (const std::runtime_error& re) {
diff --git a/lib/utils/mu-sexp.hh b/lib/utils/mu-sexp.hh
index 57ca3607..d570efcb 100644
--- a/lib/utils/mu-sexp.hh
+++ b/lib/utils/mu-sexp.hh
@@ -41,10 +41,13 @@ namespace Mu {
  * A structure somewhat similar to a Lisp s-expression and which can be
  * constructed from/to an s-expressing string representation.
  *
- * A sexp is either an atom (String, Number Symbol) or a List
+ * A sexp is either an atom (String, Number, Symbol) or a List.
  */
 struct Sexp {
-	/// Types
+	/**
+	 * Types
+	 *
+	 */
 	using	List   = std::vector<Sexp>;
 	using	String = std::string;
 	using   Number = int64_t;
@@ -64,6 +67,83 @@ struct Sexp {
 	enum struct Type { List, String, Number, Symbol };
 	using ValueType = std::variant<List, String, Number, Symbol>;
 
+	/**
+	 * Is some Sexp of the given type?
+	 *
+	 * @return true or false
+	 */
+	constexpr bool stringp() const { return std::holds_alternative<String>(value); }
+	constexpr bool numberp() const { return std::holds_alternative<Number>(value); }
+	constexpr bool listp()   const { return std::holds_alternative<List>(value); }
+	constexpr bool symbolp() const { return std::holds_alternative<Symbol>(value); }
+	constexpr bool symbolp(const Sexp::Symbol& sym) const {return symbolp() && symbol() == sym; }
+	constexpr bool nilp() const { return symbolp(nil_sym); }
+
+	// Get the specific variant type.
+	const List& list() const     { return std::get<List>(value); }
+	List& list()                 { return std::get<List>(value); }
+	const String& string() const { return std::get<String>(value); }
+	String& string()             { return std::get<String>(value); }
+	const Number& number() const { return std::get<Number>(value); }
+	Number& number()             { return std::get<Number>(value); }
+	const Symbol& symbol() const { return std::get<Symbol>(value); }
+	Symbol& symbol()             { return std::get<Symbol>(value); }
+
+	/**
+	 * Constructors
+	 */
+	Sexp():value{List{}} {} // default: an empty list.
+	// Copy & move ctors
+	Sexp(const Sexp& other):value{other.value}{}
+	Sexp(Sexp&& other):value{std::move(other.value)}{}
+	// From various types
+	Sexp(const List& lst): value{lst} {}
+	Sexp(List&& lst): value{std::move(lst)} {}
+	Sexp(const String& str): value{str} {}
+	Sexp(String&& str): value{std::move(str)} {}
+	Sexp(const char *str): Sexp{std::string{str}} {}
+	Sexp(std::string_view sv): Sexp{std::string{sv}} {}
+
+	template<typename N, typename = std::enable_if_t<std::is_integral_v<N>> >
+	Sexp(N n):value{static_cast<Number>(n)} {}
+
+	Sexp(const Symbol& sym): value{sym} {}
+	Sexp(Symbol&& sym): value{std::move(sym)} {}
+
+	template<typename S, typename T, typename... Args>
+	Sexp(S&& s, T&& t, Args&&... args): value{List()} {
+		auto& l{std::get<List>(value)};
+		l.emplace_back(Sexp(std::forward<S>(s)));
+		l.emplace_back(Sexp(std::forward<T>(t)));
+		(l.emplace_back(Sexp(std::forward<Args>(args))), ...);
+	}
+
+	/**
+	 * Copy-assignment
+	 *
+	 * @param rhs another sexp
+	 *
+	 * @return the sexp
+	 */
+	Sexp& operator=(const Sexp& rhs) {
+		if (this != &rhs)
+			value = rhs.value;
+		return *this;
+	}
+
+	/**
+	 * Move-assignment
+	 *
+	 * @param rhs another sexp
+	 *
+	 * @return the sexp
+	 */
+	Sexp& operator=(Sexp&& rhs) {
+		if (this != &rhs)
+			value = std::move(rhs.value);
+		return *this;
+	}
+
 	/**
 	 * Get the type of value
 	 *
@@ -92,70 +172,6 @@ struct Sexp {
 		}
 	}
 
-	constexpr bool stringp() const { return std::holds_alternative<String>(value); }
-	constexpr bool numberp() const { return std::holds_alternative<Number>(value); }
-	constexpr bool listp()   const { return std::holds_alternative<List>(value); }
-	constexpr bool symbolp() const { return std::holds_alternative<Symbol>(value); }
-
-	constexpr bool symbolp(const Sexp::Symbol& sym) const {return symbolp() && symbol() == sym; }
-
-	constexpr bool nilp() const { return symbolp() && symbol() == "nil"; }
-	static const Sexp& nil() { static const Sexp nilsym(Symbol{"nil"}); return nilsym; }
-	static const Sexp& t()   { static const Sexp tsym(Symbol{"t"}); return tsym; }
-
-	// Get the specific variant type.
-	const List& list() const     { return std::get<List>(value); }
-	List& list()                 { return std::get<List>(value); }
-	const String& string() const { return std::get<String>(value); }
-	String& string()             { return std::get<String>(value); }
-	const Number& number() const { return std::get<Number>(value); }
-	Number& number()             { return std::get<Number>(value); }
-	const Symbol& symbol() const { return std::get<Symbol>(value); }
-	Symbol& symbol()             { return std::get<Symbol>(value); }
-
-	/// Default ctor
-	Sexp():value{List{}} {} // default: an empty list.
-
-	// Copy & move ctors
-	Sexp(const Sexp& other):value{other.value}{}
-	Sexp(Sexp&& other):value{std::move(other.value)}{}
-
-	// Assignment
-	Sexp& operator=(const Sexp& rhs) {
-		if (this != &rhs)
-			value = rhs.value;
-		return *this;
-	}
-	Sexp& operator=(Sexp&& rhs) {
-		if (this != &rhs)
-			value = std::move(rhs.value);
-		return *this;
-	}
-
-	/// Type specific ctors
-	Sexp(const List& lst): value{lst} {}
-	Sexp(List&& lst): value{std::move(lst)} {}
-
-	Sexp(const String& str): value{str} {}
-	Sexp(String&& str): value{std::move(str)} {}
-	Sexp(const char *str): Sexp{std::string{str}} {}
-	Sexp(std::string_view sv): Sexp{std::string{sv}} {}
-
-	template<typename N, typename = std::enable_if_t<std::is_integral_v<N>> >
-	Sexp(N n):value{static_cast<Number>(n)} {}
-
-	Sexp(const Symbol& sym): value{sym} {}
-	Sexp(Symbol&& sym): value{std::move(sym)} {}
-
-	///
-	template<typename S, typename T, typename... Args>
-	Sexp(S&& s, T&& t, Args&&... args): value{List()} {
-		auto& l{std::get<List>(value)};
-		l.emplace_back(Sexp(std::forward<S>(s)));
-		l.emplace_back(Sexp(std::forward<T>(t)));
-		(l.emplace_back(Sexp(std::forward<Args>(args))), ...);
-	}
-
 	/**
 	 * Parse sexp from string
 	 *
@@ -166,12 +182,14 @@ struct Sexp {
 	static Result<Sexp> parse(const std::string& str);
 
 
-	/// List specific
+	/**
+	 * List specific functionality
+	 *
+	 */
 	using	iterator       = List::iterator;
 	using	const_iterator = List::const_iterator;
 
-
-	iterator       begin()        { return list().begin(); }
+	iterator begin()        { return list().begin(); }
 	const_iterator begin()  const { return list().begin(); }
 	const_iterator cbegin() const { return list().cbegin(); }
 
@@ -179,19 +197,6 @@ struct Sexp {
 	const_iterator end()   const { return list().end(); }
 	const_iterator cend()  const { return list().cend(); }
 
-
-	Sexp& front() { return list().front(); }
-	const Sexp& front() const { return list().front(); }
-	void pop_front() { list().erase(list().begin()); }
-
-	Option<Sexp&> head() { if (listp()&&!empty()) return front(); else return Nothing; }
-	Option<const Sexp&> head() const { if (listp()&&!empty()) return front(); else return Nothing; }
-
-	Option<Sexp&> tail() {
-		if (listp()&&!empty()&&cbegin()+1!=cend()) return *(begin()+1); else return Nothing; }
-	Option<const Sexp&> tail() const {
-		if (listp()&&!empty()&&cbegin()+1!=cend()) return *(cbegin()+1); else return Nothing; }
-
 	bool empty() const { return list().empty(); }
 	size_t size() const { return list().size(); }
 	void clear() { list().clear(); }
@@ -208,7 +213,37 @@ struct Sexp {
 			.add(std::forward<Args>(args)...);
 	}
 
-	// Plist (property lists)
+	/// Adding list elements
+	Sexp& add_list(Sexp&& l) { for (auto&& e: l) add(std::move(e)); return *this;};
+
+	/// Use list as stack.
+	Sexp& prepend(Sexp&& e) { list().insert(list().begin(), std::move(e)); return *this;};
+	Sexp& prepend(const Sexp& e) { list().insert(list().begin(), e); return *this;};
+
+	/// Some convenience for the query parser
+	Sexp& front() { return list().front(); }
+	const Sexp& front() const { return list().front(); }
+	void pop_front() { list().erase(list().begin()); }
+
+	Option<Sexp&> head() { if (listp()&&!empty()) return front(); else return Nothing; }
+	Option<const Sexp&> head() const { if (listp()&&!empty()) return front(); else return Nothing; }
+
+	bool head_symbolp() const {
+		if (auto&& h{head()}; h) return h->symbolp(); else return false;
+	}
+	bool head_symbolp(const Symbol& sym) const {
+		if (head_symbolp()) return head()->symbolp(sym); else return false;
+	}
+	Option<Sexp&> tail() {
+		if (listp()&&!empty()&&cbegin()+1!=cend()) return *(begin()+1); else return Nothing; }
+	Option<const Sexp&> tail() const {
+		if (listp()&&!empty()&&cbegin()+1!=cend()) return *(cbegin()+1); else return Nothing; }
+
+
+	/**
+	 * Property lists (aka plists)
+	 */
+
 	bool plistp() const { return listp() && plistp(cbegin(), cend()); }
 	Sexp& put_props() { return *this; } // Final case for template pack.
 	template <class PropType, class SexpType, typename... Args>
@@ -225,18 +260,14 @@ struct Sexp {
 	 *
 	 * @param p property name
 	 *
-	 * @return the property if found, or the symbol nil otherwise.
+	 * @return the property if found, or nothing
 	 */
-	const Sexp& get_prop(const std::string& p) const {
+	const Option<const Sexp&> get_prop(const std::string& p) const {
 		if (auto&& it = find_prop(p, cbegin(), cend()); it != cend())
 			return *(std::next(it));
 		else
-			return Sexp::nil();
+			return Nothing;
 	}
-	bool has_prop(const std::string& s) const {
-		return find_prop(s, cbegin(), cend())!= cend();
-	}
-
 	/// Output to string
 	enum struct Format {
 		Default	  = 0,	/**< Nothing in particular */
@@ -253,6 +284,14 @@ struct Sexp {
 	std::string to_json_string(Format fopts=Format::Default) const;
 
 	Sexp& del_prop(const std::string& pname);
+
+	/**
+	 * Some useful constants
+	 *
+	 */
+	static inline const auto nil_sym	= Sexp::Symbol{"nil"};
+	static inline const auto t_sym	= Sexp::Symbol{"t"};
+
 protected:
 	const_iterator find_prop(const std::string& s, const_iterator b,
 				       const_iterator e)  const;
@@ -261,6 +300,8 @@ private:
 	iterator find_prop(const std::string& s,iterator b,
 				 iterator e);
 	ValueType value;
+
+
 };
 
 MU_ENABLE_BITOPS(Sexp::Format);