diff --git a/language/interpreter.cc b/language/interpreter.cc
index 0f0f7aa..12d0a8a 100644
--- a/language/interpreter.cc
+++ b/language/interpreter.cc
@@ -1,5 +1,6 @@
 #include "interpreter.hpp"
 #include "parser.hpp"
+#include <sstream>
 
 using namespace peglib;
 using namespace std;
@@ -187,19 +188,28 @@ std::ostream& operator<<(std::ostream& os, const Value& val)
     return val.out(os);
 }
 
-bool run(Env& env, const char* expr, size_t len, Value& val, std::string& msg, bool print_ast)
+bool run(const string& path, Env& env, const char* expr, size_t len, Value& val, std::string& msg, bool print_ast)
 {
     try {
         shared_ptr<Ast> ast;        
-        if (get_parser().parse_n(expr, len, ast)) {
+
+        auto& parser = get_parser();
+
+        parser.log = [&](size_t ln, size_t col, const string& err_msg) {
+            stringstream ss;
+            ss << path << ":" << ln << ":" << col << ": " << err_msg << endl;
+            msg = ss.str();
+        };
+
+        if (parser.parse_n(expr, len, ast)) {
             if (print_ast) {
                 ast->print();
             }
 
             val = Eval::eval(*ast, env);
             return true;
-	     }
-    } catch (exception& e) {
+        }
+    } catch (runtime_error& e) {
         msg = e.what();
     }
 
diff --git a/language/interpreter.hpp b/language/interpreter.hpp
index d7555ca..a72d829 100644
--- a/language/interpreter.hpp
+++ b/language/interpreter.hpp
@@ -193,4 +193,4 @@ private:
     std::map<std::string, Value> dic_;
 };
 
-bool run(Env& env, const char* expr, size_t len, Value& val, std::string& msg, bool print_ast);
+bool run(const std::string& path, Env& env, const char* expr, size_t len, Value& val, std::string& msg, bool print_ast);
diff --git a/language/main.cc b/language/main.cc
index 032d72c..376dd81 100644
--- a/language/main.cc
+++ b/language/main.cc
@@ -44,27 +44,31 @@ int main(int argc, const char** argv)
         shell = path_list.empty();
     }
 
-    Env env;
-    env.setup_built_in_functions();
+    try {
+        Env env;
+        env.setup_built_in_functions();
 
-    for (auto path: path_list) {
-        vector<char> buff;
-        if (!read_file(path, buff)) {
-            cerr << "can't open '" << path << "'." << endl;
-            return -1;
+        for (auto path: path_list) {
+            vector<char> buff;
+            if (!read_file(path, buff)) {
+                cerr << "can't open '" << path << "'." << endl;
+                return -1;
+            }
+
+            Value val;
+            string msg;
+            if (!run(path, env, buff.data(), buff.size(), val, msg, print_ast)) {
+                cerr << msg;
+                return -1;
+            }
         }
 
-        Value val;
-        string msg;
-        if (!run(env, buff.data(), buff.size(), val, msg, print_ast)) {
-            cerr << "error in '" << path << "'." << endl;
-            cerr << msg.c_str() << endl;
-            return -1;
+        if (shell) {
+            repl(env, print_ast);
         }
-    }
-
-    if (shell) {
-        repl(env, print_ast);
+    } catch (exception& e) {
+        cerr << e.what() << endl;
+        return -1;
     }
 
     return 0;
diff --git a/language/parser.cc b/language/parser.cc
index 23f9068..2ab992f 100644
--- a/language/parser.cc
+++ b/language/parser.cc
@@ -40,33 +40,46 @@ static auto g_grammar = R"(
     Comment             <-  '/*' (!'*/' .)* '*/' /  ('#' / '//') (!(EndOfLine / EndOfFile) .)* (EndOfLine / EndOfFile)
 )";
 
-static auto g_parser = peg(g_grammar)
-    .ast_node_optimizable("STATEMENTS", Statements)
-    .ast_node("WHILE", While)
-    .ast_node("ASSIGNMENT", Assignment)
-    .ast_node("IF", If)
-    .ast_node("FUNCTION", Function)
-    .ast_node("PARAMETERS")
-    .ast_node("FUNCTION_CALL", FunctionCall)
-    .ast_node("ARGUMENTS")
-    .ast_node_optimizable("PRIMARY", Condition)
-    .ast_node_optimizable("CONDITION", BinExpresion)
-    .ast_node_optimizable("TERM", BinExpresion)
-    .ast_token("CONDITION_OPERATOR")
-    .ast_token("TERM_OPERATOR")
-    .ast_token("FACTOR_OPERATOR")
-    .ast_token("NUMBER", Number)
-    .ast_token("BOOLEAN", Boolean)
-    .ast_token("STRING")
-    .ast_token("IDENTIFIER", Identifier)
-    .ast_end()
-    .set_logger([&](size_t ln, size_t col, const string& msg) {
-        cerr << ln << ":" << col << ": " << msg << endl;
-    });
-
-const peglib::peg& get_parser()
+peglib::peg& get_parser()
 {
-    return g_parser;
+    static peg parser;
+
+    static bool initialized = false;
+
+    if (!initialized) {
+        initialized = true;
+
+        parser.log = [&](size_t ln, size_t col, const string& msg) {
+            cerr << ln << ":" << col << ": " << msg << endl;
+        };
+
+        if (!parser.load_grammar(g_grammar)) {
+            throw logic_error("invalid peg grammar");
+        }
+
+        parser
+            .ast_node_optimizable("STATEMENTS", Statements)
+            .ast_node("WHILE", While)
+            .ast_node("ASSIGNMENT", Assignment)
+            .ast_node("IF", If)
+            .ast_node("FUNCTION", Function)
+            .ast_node("PARAMETERS")
+            .ast_node("FUNCTION_CALL", FunctionCall)
+            .ast_node("ARGUMENTS")
+            .ast_node_optimizable("PRIMARY", Condition)
+            .ast_node_optimizable("CONDITION", BinExpresion)
+            .ast_node_optimizable("TERM", BinExpresion)
+            .ast_token("CONDITION_OPERATOR")
+            .ast_token("TERM_OPERATOR")
+            .ast_token("FACTOR_OPERATOR")
+            .ast_token("NUMBER", Number)
+            .ast_token("BOOLEAN", Boolean)
+            .ast_token("STRING")
+            .ast_token("IDENTIFIER", Identifier)
+            .ast_end();
+    }
+
+    return parser;
 }
 
 // vim: et ts=4 sw=4 cin cino={1s ff=unix
diff --git a/language/parser.hpp b/language/parser.hpp
index dee8a6f..fc1c9e2 100644
--- a/language/parser.hpp
+++ b/language/parser.hpp
@@ -6,6 +6,6 @@ enum AstType
    Identifier, Number, Boolean, Function
 };
 
-const peglib::peg& get_parser();
+peglib::peg& get_parser();
 
 // vim: et ts=4 sw=4 cin cino={1s ff=unix
diff --git a/language/repl.cc b/language/repl.cc
index 590d66b..688b18a 100644
--- a/language/repl.cc
+++ b/language/repl.cc
@@ -16,11 +16,11 @@ int repl(Env& env, bool print_ast)
         if (!line.empty()) {
             Value val;
             string msg;
-            if (run(env, line.c_str(), line.size(), val, msg, print_ast)) {
+            if (run("(repl)", env, line.c_str(), line.size(), val, msg, print_ast)) {
                 cout << val << endl;
                 linenoise::AddHistory(line.c_str());
             } else if (!msg.empty()) {
-                cout << msg << endl;
+                cout << msg;
             }
         }
     }