diff --git a/src/buildvalue.c b/src/buildvalue.c
index dff09b7..6df12d4 100644
--- a/src/buildvalue.c
+++ b/src/buildvalue.c
@@ -171,10 +171,6 @@ static Object *walkListValue(const char *fmt, int *i, va_list va, Heap *heap, Er
 
 static Object *walkValue(const char *fmt, int *i, va_list va, Heap *heap, Error *error)
 {
-	int i_;
-	if(i == NULL)
-		i = &i_;
-
 	while(isspace(fmt[*i]))
 		*i += 1;
 
@@ -222,16 +218,21 @@ static Object *walkValue(const char *fmt, int *i, va_list va, Heap *heap, Error
 				if(fmt[*i] == '\0')
 					{
 						// ERROR: Format ended inside of ${..}.
+						Error_Report(error, 0, "Format ended inside ${..}");
 						return NULL;
 					}
 
-				int end = fmt[*i];
+				assert(fmt[*i] == '}');
+
+				int end = *i;
 
 				// NOTE: The last '}' is skipped after the switch.
 				
 				const char *src = fmt + start;
 				int         len = end - start;
-					
+
+				printf("src: [%.*s]\n", len, src);
+				
 				o = eval(src, len, NULL, heap, error);
 
 				if(o == NULL)
@@ -281,7 +282,8 @@ static Object *walkValue(const char *fmt, int *i, va_list va, Heap *heap, Error
 
 Object *buildValue2(Heap *heap, Error *error, const char *fmt, va_list va)
 {
-	return walkValue(fmt, NULL, va, heap, error);
+	int i = 0;
+	return walkValue(fmt, &i, va, heap, error);
 }
 
 Object *buildValue(Heap *heap, Error *error, const char *fmt, ...)
diff --git a/src/eval.c b/src/eval.c
index 213c11c..d83d2d5 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1,3 +1,4 @@
+#include <string.h>
 #include "compiler/parse.h"
 #include "compiler/compile.h"
 #include "runtime/runtime.h"
@@ -6,6 +7,9 @@
 
 Object *eval(const char *str, int len, Object *closure, Heap *heap, Error *error)
 {
+	if(len < 0)
+		len = strlen(str);
+
 	Source *s = Source_FromString(NULL, str, len, error);
 
 	if(s == NULL)
diff --git a/src/main.c b/src/main.c
index 5179436..fa17a04 100644
--- a/src/main.c
+++ b/src/main.c
@@ -103,11 +103,35 @@ static int parse_args(Options *opts, int argc, char **argv, Error *error)
 	return i;
 }
 
+#include "buildvalue.h"
+
 int main(int argc, char **argv)
 {
 	Error error;
 	Error_Init(&error);
 
+	{
+		Heap *heap = Heap_New(-1);
+
+		if(heap == NULL)
+			{
+				fprintf(stderr, "ERROR: Failed to create heap.\n");
+				return -1;
+			}
+
+		Object *o = buildValue(heap, &error, "${ return 3+1; }");
+	
+		if(o == NULL)
+			{
+				fprintf(stderr, "ERROR: %s.\n", error.message);
+				return -1;
+			}
+
+		Object_Print(o, stdout);
+
+		Heap_Free(heap);
+	}
+
 
 	// Parse command line options.