diff --git a/lambdex/__init__.py b/lambdex/__init__.py
index d5130e8..4425c69 100644
--- a/lambdex/__init__.py
+++ b/lambdex/__init__.py
@@ -1,17 +1,49 @@
 import os
 import sys
 
-f = sys._getframe(1)
-while f.f_code is not None and f.f_code.co_filename.startswith('<'):
-    f = f.f_back
 
-if f and f.f_code and f.f_code.co_filename.startswith(os.path.dirname(os.__file__)):
+def _is_run_as_script():
+    """
+    Check that whether lambdex is run as top-level script.
+
+    We iterate from the stack bottom to find the first frame that contains
+    no 'importlib' string, which should be the importer of lambdex.
+
+    If the importer has any system prefixes, we assert that lambdex is run
+    as top-level script.
+    """
+    import site
+    from os.path import dirname, abspath
+
+    f = sys._getframe(1)
+    while f is not None \
+        and f.f_code is not None \
+        and 'importlib' in f.f_code.co_filename:
+        f = f.f_back
+
+    if not (f or f.f_code):
+        return False
+
+    filename = abspath(f.f_code.co_filename)
+    for sitepath in site.getsitepackages() + [site.getusersitepackages()]:
+        prefix = dirname(dirname(dirname(sitepath)))  # such as '/usr/local'
+        if filename.startswith(prefix):
+            return True
+
+    return False
+
+
+# If run as top-level script, user is happened to use lxfmt.
+# We remove CWD from sys.path, so that the files user editting will not
+# cause name conflicts with built-in modules.
+if _is_run_as_script():
     if sys.path and sys.path[0] == os.getcwd():
         sys.path = sys.path[1:]
+# Otherwise, we import keywords as normal
 else:
-    __all__ = ['def_']
-    from .keywords import def_
+    from .keywords import *
+    from .keywords import __all__
 
-del os, sys, f
+del os, sys, _is_run_as_script
 
 __version__ = "0.2.0"