diff --git a/xo-expression2/include/xo/expression2/DGlobalSymtab.hpp b/xo-expression2/include/xo/expression2/DGlobalSymtab.hpp
index bb668ff3..91117888 100644
--- a/xo-expression2/include/xo/expression2/DGlobalSymtab.hpp
+++ b/xo-expression2/include/xo/expression2/DGlobalSymtab.hpp
@@ -6,6 +6,7 @@
 #pragma once
 
 #include "Binding.hpp"
+#include <xo/arena/DArenaHashMap.hpp>
 
 namespace xo {
     namespace scm {
@@ -13,10 +14,21 @@ namespace xo {
 
         /** @class DGlobalSymtab
          *  @brief symbol table for toplevel environment
+         *
+         *  We're using DArenaHashMap to store <key,binding> pairs.
+         *  Both of these are outside GC-space, so we don't need collector
+         *  to traverse these.
          **/
-        struct DGlobalSymtab {
+        class DGlobalSymtab {
         public:
+            using key_type = const DUniqueString *;
+            using value_type = Binding;
+            using repr_type = xo::map::DArenaHashMap<key_type, value_type>;
+            using MemorySizeVisitor = xo::mm::MemorySizeVisitor;
 
+        public:
+            /** visit symtab-owned memory pools; call visitor(info) for each **/
+            void visit_pools(const MemorySizeVisitor & visitor) const;
 
         public:
             /** @defgroup xo-expression2-symboltable-facet symboltable facet**/
@@ -31,6 +43,12 @@ namespace xo {
             ///@}
 
         private:
+            /** next binding will use this global index. See DGlobalEnv **/
+            uint32_t next_binding_ix_ = 0;
+
+            /** map symbols -> bindings **/
+            repr_type map_;
+            
         };
 
     } /*namespace scm*/
diff --git a/xo-interpreter2/include/xo/interpreter2/DGlobalEnv.hpp b/xo-interpreter2/include/xo/interpreter2/DGlobalEnv.hpp
index e9f1a9c8..60fbe461 100644
--- a/xo-interpreter2/include/xo/interpreter2/DGlobalEnv.hpp
+++ b/xo-interpreter2/include/xo/interpreter2/DGlobalEnv.hpp
@@ -6,26 +6,43 @@
 #pragma once
 
 #include <xo/expression2/DGlobalSymtab.hpp>
-#include <xo/object2/DList.hpp>
 #include <xo/object2/DArray.hpp>
 
 namespace xo {
     namespace scm {
 
-
         /** @brief runtime bindings for global variabels
+         *
+         *  Implementation here uses a DArenaHashMap to hold <key,value> pairs.
+         *  The hash map has its own memory outside GC space.
+         *  Keys are DUniqueStrings, also outside GC space.
+         *  Values are regular gc-aware objects, generally will be in GC space.
+         *
+         *  We need collector to traverse all the values in a global env
+         *  on each cycle.  Arrange that by having DGlobalEnv itself
+         *  in GC space.
+         *
          **/
         class DGlobalEnv {
+        public:
+            using MemorySizeVisitor = xo::mm::MemorySizeVisitor;
+
         public:
             DGlobalEnv() = default;
 
+            /** visit env-owned memory pools; call visitor(info) for each **/
+            void visit_pools(const MemorySizeVisitor & visitor) const;
+
         protected: // temporary, to appease compiler
 
             // absurd O(n) implementation for now
             // replace with gc-aware hashtable, when available.
 
-            /** globals.  Slots in @ref global_v_ are numbered in DLocalSymtab **/
-            DArray * global_v_ = nullptr;
+            /** symbol table assigns a unique index for each symbol **/
+            DGlobalSymtab * symtab_;
+
+            /** value for a symbol S will be in values_[symtab->lookup_binding(S)] **/
+            DArray * values_ = nullptr;
         };
     }
 }
diff --git a/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp b/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
index 7c31d645..960c1771 100644
--- a/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
+++ b/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
@@ -202,7 +202,8 @@ namespace xo {
         {
             const auto & testname = Catch::getResultCapture().getCurrentTestName();
 
-            scope log(XO_DEBUG(true), xtag("test", testname));
+            constexpr bool c_debug_flag = false;
+            scope log(XO_DEBUG(c_debug_flag), xtag("test", testname));
 
             VsmConfig cfg;
             VirtualSchematikaMachine vsm(cfg);
@@ -237,11 +238,52 @@ namespace xo {
             vsm.visit_pools(visitor);
         }
 
+        TEST_CASE("VirtualSchematikaMachine-if", "[interpreter2][VSM]")
+        {
+            const auto & testname = Catch::getResultCapture().getCurrentTestName();
+
+            constexpr bool c_debug_flag = true;
+            scope log(XO_DEBUG(c_debug_flag), xtag("test", testname));
+
+            VsmConfig cfg;
+            VirtualSchematikaMachine vsm(cfg);
+
+            bool eof_flag = false;
+
+            vsm.begin_interactive_session();
+            VsmResultExt res = vsm.read_eval_print(span_type::from_cstr("if 123 == 123 then \"equal\" else \"notequal\";"), eof_flag);
+
+            REQUIRE(res.is_value());
+            REQUIRE(res.value());
+
+            log && log(xtag("res.tseq", res.value()->_typeseq()));
+
+            auto x = obj<AGCObject,DBoolean>::from(*res.value());
+
+            REQUIRE(x);
+            REQUIRE(x.data()->value() == true);
+
+            REQUIRE(res.remaining_.size() == 1);
+            REQUIRE(*res.remaining_.lo() == '\n');
+
+            auto visitor = [&log](const MemorySizeInfo & info) {
+                log && log(xtag("resource", info.resource_name_),
+                           xtag("used", info.used_),
+                           xtag("alloc", info.allocated_),
+                           xtag("commit", info.committed_),
+                           xtag("resv", info.reserved_));
+            };
+
+            FacetRegistry::instance().visit_pools(visitor);
+            vsm.visit_pools(visitor);
+        }
+
         TEST_CASE("VirtualSchematikaMachine-lambda1", "[interpreter2][VSM]")
         {
             const auto & testname = Catch::getResultCapture().getCurrentTestName();
 
-            scope log(XO_DEBUG(false), xtag("test", testname));
+            constexpr bool c_debug_flag = false;
+            scope log(XO_DEBUG(c_debug_flag), xtag("test", testname));
 
             VsmConfig cfg;
             VirtualSchematikaMachine vsm(cfg);