diff --git a/backend/src/builtin-cli.cpp b/backend/src/builtin-cli.cpp
index 6679a82..361c0e7 100644
--- a/backend/src/builtin-cli.cpp
+++ b/backend/src/builtin-cli.cpp
@@ -17,10 +17,10 @@ void BookStoreMain(bool is_server, std::string config_dir) {
     std::string cmd;
     while (std::getline(std::cin, cmd)) {
       auto result = std::move(engine.Execute(cmd, login_stack));
-      // debugPrint(cmd);
+      debugPrint(cmd);
       for (auto &line : result) {
         std::cout << line << '\n';
-        // debugPrint(line);
+        debugPrint(line);
       }
       // debugPrint();
       if (BookStore_ZYM::shut_down) return;
diff --git a/backend/src/engine.cpp b/backend/src/engine.cpp
index 22250b6..4753a7f 100644
--- a/backend/src/engine.cpp
+++ b/backend/src/engine.cpp
@@ -300,11 +300,16 @@ std::vector<std::string> BookStoreEngineClass::ExecuteMOdify(
   double price;
   if (!CommandModifyLexer(cmd, new_ISBN, name, author, keyword, price))
     return std::vector<std::string>({"Invalid"});
+  // debugPrint("successfully lexed modify");
+  // debugPrint("modify", new_ISBN, ' ', name, ' ', author, ' ', keyword, ' ',
+            //  price);
   if (login_stack.empty() ||
       user_data_base.GetPrevilege(login_stack.top().first) < 3)
     return std::vector<std::string>({"Invalid"});
+  // debugPrint("successfully checked authority");
   if (login_stack.top().second == "" || login_stack.top().second == new_ISBN)
     return std::vector<std::string>({"Invalid"});
+  // debugPrint("successfully checked ISBN");
   if (keyword != "") {
     std::vector<std::string> key_list;
     if (!KeyWordSpliter(keyword, key_list, false))
@@ -316,6 +321,7 @@ std::vector<std::string> BookStoreEngineClass::ExecuteMOdify(
       key_set.insert(i);
     }
   }
+  // debugPrint("successfully checked keyword");
   book_data_base.ModifyInfo(login_stack.top().second, new_ISBN, name, author,
                             keyword, price, -1);
   return std::vector<std::string>();
diff --git a/backend/src/lexer.cpp b/backend/src/lexer.cpp
index 7935f9d..658f5a3 100644
--- a/backend/src/lexer.cpp
+++ b/backend/src/lexer.cpp
@@ -1,5 +1,6 @@
 #include "lexer.h"
 
+#include "bs-utility.h"
 // clang-format off
 /**
  * @brief Lexer for command "su"
@@ -336,7 +337,7 @@ bool CommandModifyLexer(const std::string &command, std::string &ISBN,
                         std::string &name, std::string &author,
                         std::string &keyword, double &price) {
   static std::basic_regex main_pattern(
-      R"(^ *modify(?: +-ISBN=(?:\S{1,20})| +-name=\"(?:[^\s"]{1,60})\"| +-author=\"(?:[^\s"]{1,60})\"| +-keyword=\"(?:[^\s"]{1,60})\"| +-price=[0-9]{1,10}\.[0-9]{2})+ *$)",
+      R"(^ *modify(?: +-ISBN=(?:\S{1,20})| +-name=\"(?:[^\s"]{1,60})\"| +-author=\"(?:[^\s"]{1,60})\"| +-keyword=\"(?:[^\s"]{1,60})\"| +-price=[0-9]{1,10}(?:\.[0-9]{1,2})?)+ *$)",
       std::regex_constants::optimize);
   if (std::regex_match(command, main_pattern)) {
     std::stringstream ss(command);
@@ -349,6 +350,7 @@ bool CommandModifyLexer(const std::string &command, std::string &ISBN,
     price = -1;
     while (ss >> token) {
       if (token[1] == 'I') {
+        // debugPrint("ISBN's token is ", token);
         ISBN = token.substr(6);
       } else if (token[1] == 'n') {
         name = token.substr(6 + 1, token.size() - 7 - 1);
@@ -383,7 +385,7 @@ bool CommandModifyLexer(const std::string &command, std::string &ISBN,
 bool CommandImportLexer(const std::string &command, int &quantity,
                         double &total_cost) {
   static std::basic_regex main_pattern(
-      R"(^ *import +[0-9]{1,10} +[0-9]{1,10}\.[0-9]{2} *$)",
+      R"(^ *import +[0-9]{1,10} +[0-9]{1,10}(?:\.[0-9]{1,2})? *$)",
       std::regex_constants::optimize);
   if (std::regex_match(command, main_pattern)) {
     std::stringstream ss(command);