diff --git a/xo-expression2/include/xo/expression2/DDefineExpr.hpp b/xo-expression2/include/xo/expression2/DDefineExpr.hpp
index 94a37197..618e4161 100644
--- a/xo-expression2/include/xo/expression2/DDefineExpr.hpp
+++ b/xo-expression2/include/xo/expression2/DDefineExpr.hpp
@@ -25,6 +25,9 @@ namespace xo {
             using TypeDescr = xo::reflect::TypeDescr;
 
         public:
+            /** @defgroup scm-defineexpr-constructors **/
+            ///@{
+
             /** create instance: define-expr using memory from @p mm
              *  with lhs name @p lhs_name and rhs expression @p rhs_expr
              **/
@@ -35,14 +38,20 @@ namespace xo {
              **/
             static DDefineExpr * make_empty(obj<AAllocator> mm);
 
+            DDefineExpr(DVariable * lhs_var,
+                        obj<AExpression> rhs);
+
+            ///@}
+            /** @defgroup scm-definexpr-access-methods **/
+            ///@{
+
             DVariable * lhs() const { return lhs_var_; }
             obj<AExpression> rhs() const noexcept { return rhs_; }
-
             const DUniqueString * name() const noexcept;
 
             void assign_lhs_name(const DUniqueString * name);
-            /** CONCESSION.  will use DUniqueString* once we have StringTable **/
-            void assign_lhs_name(std::string_view name);
+
+            ///@}
 
             /** @defgroup scm-defineexpr-expression-facet **/
             ///@{
@@ -55,10 +64,9 @@ namespace xo {
             ///@}
 
         private:
-            DDefineExpr(DVariable * lhs_var,
-                        obj<AExpression> rhs);
+            /** @defgrouop scm-defineexpr-instance-vars **/
+            ///@{
 
-        private:
             /** variable being defined by this expression.
              **/
             DVariable * lhs_var_ = nullptr;
@@ -68,6 +76,8 @@ namespace xo {
             obj<AExpression> rhs_;
 
             // std::set<std::string> free_var_set_;
+
+            ///@}
         };
     } /*namespace scm*/
 } /*namespace xo*/
diff --git a/xo-expression2/src/expression2/DDefineExpr.cpp b/xo-expression2/src/expression2/DDefineExpr.cpp
index ada633f6..a5609246 100644
--- a/xo-expression2/src/expression2/DDefineExpr.cpp
+++ b/xo-expression2/src/expression2/DDefineExpr.cpp
@@ -55,15 +55,6 @@ namespace xo {
             lhs_var_->assign_name(name);
         }
 
-        void
-        DDefineExpr::assign_lhs_name(std::string_view name)
-        {
-            scope log(XO_DEBUG(true), "bogus impl - will require unique string");
-            log && log(xtag("name", name));
-
-            //lhs_var_->assign_name(name);
-        }
-
         void
         DDefineExpr::assign_valuetype(TypeDescr td) noexcept
         {
diff --git a/xo-reader2/include/xo/reader2/ParserStateMachine.hpp b/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
index fb276bd0..b333dd51 100644
--- a/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
+++ b/xo-reader2/include/xo/reader2/ParserStateMachine.hpp
@@ -69,6 +69,10 @@ namespace xo {
             /** pop syntax state machine from top of @ref stack_ **/
             void pop_ssm();
 
+            /** get unique string copy of @p str. Idempotent for each @p str.
+             **/
+            const DUniqueString * intern_string(std::string_view str);
+
             /** add variable to current local environment (innermost lexical scope) **/
             void upsert_var(DVariable * var);
 
diff --git a/xo-reader2/src/reader2/DDefineSsm.cpp b/xo-reader2/src/reader2/DDefineSsm.cpp
index adf9f429..eabc1868 100644
--- a/xo-reader2/src/reader2/DDefineSsm.cpp
+++ b/xo-reader2/src/reader2/DDefineSsm.cpp
@@ -412,12 +412,15 @@ namespace xo {
         }
 
         void
-        DDefineSsm::on_parsed_symbol(std::string_view sym,
+        DDefineSsm::on_parsed_symbol(std::string_view sym_name,
                                      ParserStateMachine * p_psm)
         {
             if (this->defstate_ == defexprstatetype::def_1) {
                 this->defstate_ = defexprstatetype::def_2;
 
+                const DUniqueString * sym
+                    = p_psm->intern_string(sym_name);
+
                 def_expr_.data()->assign_lhs_name(sym);
 
                 // if this is a genuine top-level define (i.e. nesting level = 0),
@@ -448,7 +451,7 @@ namespace xo {
             }
 
             p_psm->illegal_input_on_symbol("DDefineSsm::on_parsed_symbol",
-                                           sym,
+                                           sym_name,
                                            this->get_expect_str());
         }
 
diff --git a/xo-reader2/src/reader2/ParserStateMachine.cpp b/xo-reader2/src/reader2/ParserStateMachine.cpp
index 1766f652..ca8bba8b 100644
--- a/xo-reader2/src/reader2/ParserStateMachine.cpp
+++ b/xo-reader2/src/reader2/ParserStateMachine.cpp
@@ -73,6 +73,12 @@ namespace xo {
             this->stack_ = ParserStack::pop(stack_, parser_alloc_);
         }
 
+        const DUniqueString *
+        ParserStateMachine::intern_string(std::string_view str)
+        {
+            return stringtable_.intern(str);
+        }
+
         void
         ParserStateMachine::upsert_var(DVariable * var)
         {