diff --git a/client/main.c b/client/main.c
index 9af9a177..05338763 100644
--- a/client/main.c
+++ b/client/main.c
@@ -29,12 +29,13 @@
 #include <gst/disasm.h>
 
 /* Compile and run an ast */
-int debug_compile_and_run(Gst *vm, GstValue ast) {
+int debug_compile_and_run(Gst *vm, GstValue ast, GstValue env) {
     GstCompiler c;
     GstValue func;
     /* Try to compile generated AST */
     gst_compiler(&c, vm);
     gst_compiler_usemodule(&c, "std");
+    gst_compiler_globals(&c, env);
     func = gst_wrap_function(gst_compiler_compile(&c, ast));
     /* Check for compilation errors */
     if (c.error) {
@@ -92,7 +93,7 @@ int debug_run(Gst *vm, FILE *in) {
         printf("Unexpected end of source\n");
         return 1;
     }
-    return debug_compile_and_run(vm, ast);
+    return debug_compile_and_run(vm, ast, gst_wrap_nil());
 }
 
 /* A simple repl */
@@ -100,6 +101,7 @@ int debug_repl(Gst *vm) {
     char buffer[1024] = {0};
     const char *reader = buffer;
     GstParser p;
+    GstValue *st;
     int reset;
     for (;;) {
         /* Init parser */
@@ -127,7 +129,10 @@ int debug_repl(Gst *vm) {
             printf("Unexpected end of source\n");
             continue;
         }
-        if (0 == debug_compile_and_run(vm, gst_parse_consume(&p))) {
+        /* Add _ to environemt */
+        st = gst_struct_begin(vm, 1);
+        gst_struct_put(st, gst_string_cv(vm, "_"), vm->ret);
+        if (0 == debug_compile_and_run(vm, gst_parse_consume(&p), gst_wrap_struct(gst_struct_end(vm, st)))) {
             printf("%s\n", gst_to_string(vm, vm->ret));
         }
     }
diff --git a/core/compile.c b/core/compile.c
index 6d3abb19..7c6e71e0 100644
--- a/core/compile.c
+++ b/core/compile.c
@@ -1072,7 +1072,7 @@ void gst_compiler_globals(GstCompiler *c, GstValue env) {
 
 /* Use a module that was loaded into the vm */
 void gst_compiler_usemodule(GstCompiler *c, const char *modulename) {
-    GstValue mod = gst_object_get(c->vm->rootenv, gst_string_cv(c->vm, modulename));
+    GstValue mod = gst_object_get(c->vm->modules, gst_string_cv(c->vm, modulename));
     gst_compiler_globals(c, mod);
 }
 
diff --git a/core/gc.c b/core/gc.c
index cc9dc844..dea231a9 100644
--- a/core/gc.c
+++ b/core/gc.c
@@ -264,19 +264,14 @@ void gst_mem_tag(void *mem, uint32_t tags) {
 
 /* Run garbage collection */
 void gst_collect(Gst *vm) {
-    GstValueUnion renv;
     /* Thread can be null */
-    if (vm->thread) {
-        GstValueUnion t;
-        t.thread = vm->thread;
-        gst_mark(vm, t, GST_THREAD);
-    }
-    renv.object = vm->rootenv;
-    gst_mark(vm, renv, GST_OBJECT);
+    if (vm->thread)
+        gst_mark_value(vm, gst_wrap_thread(vm->thread));
+    gst_mark_value(vm, gst_wrap_object(vm->modules));
+    gst_mark_value(vm, gst_wrap_object(vm->registry));
     gst_mark_value(vm, vm->ret);
-    if (vm->scratch) {
+    if (vm->scratch)
         gc_header(vm->scratch)->color = vm->black;
-    }
     gst_sweep(vm);
     vm->nextCollection = 0;
 }
diff --git a/core/stl.c b/core/stl.c
index 50b68a70..d6df5300 100644
--- a/core/stl.c
+++ b/core/stl.c
@@ -414,18 +414,19 @@ int gst_stl_serialize(Gst *vm) {
 /* TODO - add userdata to allow for manipulation of FILE pointers. */
 
 int gst_stl_open(Gst *vm) {
-    GstValue ret;
     const uint8_t *fname = gst_to_string(vm, gst_arg(vm, 0));
     const uint8_t *fmode = gst_to_string(vm, gst_arg(vm, 1));
     FILE *f;
+    FILE **fp;
+    GstValue *st;
     if (gst_count_args(vm) < 2)
         gst_c_throwc(vm, "expected filename and filemode");
     f = fopen((const char *)fname, (const char *)fmode);
     if (!f)
         gst_c_throwc(vm, "could not open file");
-    ret.type = GST_USERDATA;
-    ret.data.pointer = f;
-    gst_c_return(vm, ret);
+    st = gst_struct_begin(vm, 0);
+    fp = gst_userdata(vm, sizeof(FILE *), gst_struct_end(vm, st));
+    gst_c_return(vm, gst_wrap_userdata(fp));
 }
 
 /****/
@@ -464,5 +465,5 @@ static const GstModuleItem const std_module[] = {
 
 /* Load all libraries */
 void gst_stl_load(Gst *vm) {
-    gst_c_register(vm, "std", gst_c_module_struct(vm, std_module));
+    gst_module_put(vm, "std", gst_cmodule_struct(vm, std_module));
 }
diff --git a/core/util.c b/core/util.c
index 844456bb..545e8462 100644
--- a/core/util.c
+++ b/core/util.c
@@ -56,7 +56,7 @@ GST_WRAP_DEFINE(funcdef, GstFuncDef *, GST_FUNCDEF, def)
 
 #undef GST_WRAP_DEFINE
 
-GstValue gst_c_module_object(Gst *vm, const GstModuleItem *mod) {
+GstValue gst_cmodule_object(Gst *vm, const GstModuleItem *mod) {
     GstObject *module = gst_object(vm, 10);
     while (mod->name != NULL) {
         GstValue key = gst_string_cv(vm, mod->name);
@@ -66,7 +66,7 @@ GstValue gst_c_module_object(Gst *vm, const GstModuleItem *mod) {
     return gst_wrap_object(module);
 }
 
-GstValue gst_c_module_struct(Gst *vm, const GstModuleItem *mod) {
+GstValue gst_cmodule_struct(Gst *vm, const GstModuleItem *mod) {
     uint32_t count = 0;
     const GstModuleItem *m = mod;
     GstValue *st;
@@ -86,8 +86,26 @@ GstValue gst_c_module_struct(Gst *vm, const GstModuleItem *mod) {
     
 }
 
-void gst_c_register(Gst *vm, const char *packagename, GstValue mod) {
-    if (vm->rootenv == NULL)
-        vm->rootenv = gst_object(vm, 10);
-    gst_object_put(vm, vm->rootenv, gst_string_cv(vm, packagename), mod);
+void gst_module_put(Gst *vm, const char *packagename, GstValue mod) {
+    if (vm->modules == NULL)
+        vm->modules = gst_object(vm, 10);
+    gst_object_put(vm, vm->modules, gst_string_cv(vm, packagename), mod);
+}
+
+GstValue gst_module_get(Gst *vm, const char *packagename) {
+    if (!vm->modules)
+        return gst_wrap_nil();
+    return gst_object_get(vm->modules, gst_string_cv(vm, packagename));
+}
+
+void gst_register_put(Gst *vm, const char *name, GstValue c) {
+    if (vm->registry == NULL)
+        vm->registry = gst_object(vm, 10);
+    gst_object_put(vm, vm->registry, gst_string_cv(vm, name), c);
+}
+
+GstValue gst_register_get(Gst *vm, const char *name) {
+    if (!vm->registry)
+        return gst_wrap_nil();
+    return gst_object_get(vm->registry, gst_string_cv(vm, name));
 }
diff --git a/core/vm.c b/core/vm.c
index 2749aee5..a14a2726 100644
--- a/core/vm.c
+++ b/core/vm.c
@@ -498,16 +498,17 @@ void gst_init(Gst *vm) {
     /* Garbage collection */
     vm->blocks = NULL;
     vm->nextCollection = 0;
-    /* Setting memoryInterval to zero currently forces
+    /* Setting memoryInterval to zero forces
      * a collection pretty much every cycle, which is
-     * obviously horrible for performance. It helps ensure
+     * obviously horrible for performance, but helps ensure
      * there are no memory bugs during dev */
     vm->memoryInterval = 2000;
     vm->black = 0;
     /* Add thread */
     vm->thread = NULL;
     /* Set up global env */
-    vm->rootenv = NULL;
+    vm->modules = NULL;
+    vm->registry = NULL;
     /* Set up scratch memory */
     vm->scratch = NULL;
     vm->scratch_len = 0;
@@ -522,7 +523,8 @@ void gst_init(Gst *vm) {
 void gst_deinit(Gst *vm) {
     gst_clear_memory(vm);
     vm->thread = NULL;
-    vm->rootenv = NULL;
+    vm->modules = NULL;
+    vm->registry = NULL;
     vm->ret.type = GST_NIL;
     vm->scratch = NULL;
     vm->scratch_len = 0;
diff --git a/include/gst/gst.h b/include/gst/gst.h
index c2df7acb..439ae53a 100644
--- a/include/gst/gst.h
+++ b/include/gst/gst.h
@@ -283,13 +283,13 @@ struct Gst {
     uint32_t cache_capacity;
     uint32_t cache_count;
     uint32_t cache_deleted;
-    /* Scratch memory */
+    /* Scratch memory (should be marked in gc) */
     char *scratch;
     uint32_t scratch_len;
-    /* Thread */
+    /* GC roots */
     GstThread *thread;
-    /* A GC root */
-    GstObject *rootenv;
+    GstObject *modules;
+    GstObject *registry;
     /* Return state */
     const char *crash;
     GstValue ret; /* Returned value from gst_start. Also holds errors. */
@@ -511,9 +511,12 @@ uint16_t gst_count_args(Gst *vm);
 /* C Api */
 /***/
 
-GstValue gst_c_module_object(Gst *vm, const GstModuleItem *mod);
-GstValue gst_c_module_struct(Gst *vm, const GstModuleItem *mod);
-void gst_c_register(Gst *vm, const char *packagename, GstValue mod);
+GstValue gst_cmodule_object(Gst *vm, const GstModuleItem *mod);
+GstValue gst_cmodule_struct(Gst *vm, const GstModuleItem *mod);
+void gst_module_put(Gst *vm, const char *packagename, GstValue mod);
+GstValue gst_module_get(Gst *vm, const char *packagename);
+void gst_register_put(Gst *vm, const char *packagename, GstValue mod);
+GstValue gst_register_get(Gst *vm, const char *name);
 
 /* Wrap data in GstValue */
 GstValue gst_wrap_nil();