diff --git a/example/maps.cpp b/example/maps.cpp
index 2a6991c..7b224f1 100644
--- a/example/maps.cpp
+++ b/example/maps.cpp
@@ -8,10 +8,10 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <inttypes.h>
+#include <cassert>
 #include "llvmbpf.hpp"
 
 using namespace bpftime;
-
 const unsigned char xdp_counter_bytecode[] = "\x79\x16\x00\x00\x00\x00\x00\x00"
 					     "\x79\x17\x08\x00\x00\x00\x00\x00"
 					     "\xb7\x01\x00\x00\x00\x00\x00\x00"
@@ -19,14 +19,15 @@ const unsigned char xdp_counter_bytecode[] = "\x79\x16\x00\x00\x00\x00\x00\x00"
 					     "\xbf\xa2\x00\x00\x00\x00\x00\x00"
 					     "\x07\x02\x00\x00\xfc\xff\xff\xff"
 					     "\x18\x11\x00\x00\x05\x00\x00\x00"
-					     "\x00\x00\x00\x00\x85\x00\x00\x00"
-					     "\x01\x00\x00\x00\xbf\x01\x00\x00"
-					     "\x00\x00\x00\x00\xb7\x00\x00\x00"
-					     "\x02\x00\x00\x00\x15\x01\x18\x00"
-					     "\x00\x00\x00\x00\x61\x11\x00\x00"
-					     "\x00\x00\x00\x00\x55\x01\x16\x00"
-					     "\x00\x00\x00\x00\x18\x21\x00\x00"
-					     "\x06\x00\x00\x00\x00\x00\x00\x00"
+					     "\x00\x00\x00\x00\x00\x00\x00\x00"
+					     "\x85\x00\x00\x00\x01\x00\x00\x00"
+					     "\xbf\x01\x00\x00\x00\x00\x00\x00"
+					     "\xb7\x00\x00\x00\x02\x00\x00\x00"
+					     "\x15\x01\x18\x00\x00\x00\x00\x00"
+					     "\x61\x11\x00\x00\x00\x00\x00\x00"
+					     "\x55\x01\x16\x00\x00\x00\x00\x00"
+					     "\x18\x21\x00\x00\x06\x00\x00\x00"
+					     "\x00\x00\x00\x00\x00\x00\x00\x00"
 					     "\x79\x12\x00\x00\x00\x00\x00\x00"
 					     "\x07\x02\x00\x00\x01\x00\x00\x00"
 					     "\x7b\x21\x00\x00\x00\x00\x00\x00"
@@ -52,7 +53,7 @@ const unsigned char xdp_counter_bytecode[] = "\x79\x16\x00\x00\x00\x00\x00\x00"
 uint8_t bpf_mem[] = { 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88 };
 
 uint32_t ctl_array[2] = { 0, 0 };
-uint64_t ctrn_array[2] = { 0, 0 };
+uint64_t cntrs_array[2] = { 0, 0 };
 
 void *bpf_map_lookup_elem(uint64_t map_fd, void *key)
 {
@@ -60,7 +61,7 @@ void *bpf_map_lookup_elem(uint64_t map_fd, void *key)
 	if (map_fd == 5) {
 		return &ctl_array[*(uint32_t *)key];
 	} else if (map_fd == 6) {
-		return &ctrn_array[*(uint32_t *)key];
+		return &cntrs_array[*(uint32_t *)key];
 	} else {
 		return nullptr;
 	}
@@ -69,28 +70,33 @@ void *bpf_map_lookup_elem(uint64_t map_fd, void *key)
 
 uint64_t map_by_fd(uint32_t fd)
 {
+	std::cout << "map_by_fd " << fd << std::endl;
 	return fd;
 }
 uint64_t map_by_idx(uint32_t idx)
 {
+	std::cout << "map_by_idx " << idx << std::endl;
 	return idx;
 }
 uint64_t map_val(uint64_t val)
 {
+	std::cout << "map_val " << val << std::endl;
 	if (val == 5) {
 		return (uint64_t)(void *)ctl_array;
 	} else if (val == 6) {
-		return (uint64_t)(void *)ctrn_array;
+		return (uint64_t)(void *)cntrs_array;
 	} else {
 		return 0;
 	}
 }
 uint64_t var_addr(uint32_t idx)
 {
+	std::cout << "var_addr " << idx << std::endl;
 	return idx;
 }
 uint64_t code_addr(uint32_t idx)
 {
+	std::cout << "code_addr " << idx << std::endl;
 	return idx;
 }
 
@@ -108,7 +114,7 @@ int main(int argc, char *argv[])
 			vm.get_error_message().c_str());
 		exit(1);
 	}
-	vm.register_external_function(2, "bpf_map_lookup_elem",
+	vm.register_external_function(1, "bpf_map_lookup_elem",
 				      (void *)bpf_map_lookup_elem);
 	// set the lddw helpers for accessing maps
 	vm.set_lddw_helpers(map_by_fd, map_by_idx, map_val, var_addr,
@@ -119,11 +125,24 @@ int main(int argc, char *argv[])
 			vm.get_error_message().c_str());
 		exit(1);
 	}
+	// Map value (counter) should be 0	
+	std::cout << "cntrs_array[0] = " << cntrs_array[0] << std::endl;
 	int err = vm.exec(&bpf_mem, sizeof(bpf_mem), res);
-	if (err != 0) {
-		fprintf(stderr, "Failed to exec.");
-		exit(1);
-	}
-	printf("res = %" PRIu64 "\n", res);
+	assert(err == 0 && cntrs_array[0] == 1);
+	std::cout << "\nreturn value = " << res << std::endl;
+	// counter should be 1
+	std::cout << "cntrs_array[0] = " << cntrs_array[0] << std::endl;
+
+	err = vm.exec(&bpf_mem, sizeof(bpf_mem), res);
+	assert(err == 0 && cntrs_array[0] == 2);
+	std::cout << "\nreturn value = " << res << std::endl;
+	// counter should be 2
+	std::cout << "cntrs_array[0] = " << cntrs_array[0] << std::endl;
+
+	// Change the value of the control array can change the return value
+	ctl_array[0] = 1;
+	err = vm.exec(&bpf_mem, sizeof(bpf_mem), res);
+	assert(err == 0);
+	std::cout << "\nreturn value = " << res << std::endl;
 	return 0;
 }