diff --git a/pier.py b/pier.py
index d24a721..1a33d60 100755
--- a/pier.py
+++ b/pier.py
@@ -27,12 +27,16 @@ from io import StringIO
 import os
 import sys
 import shlex
+import traceback
 import http.server
 import socketserver
 
 
 URL_SPACE = "%20"
 
+exec_globals = {}
+exec_locals = {}
+
 
 class ScriptServer(http.server.SimpleHTTPRequestHandler):
 
@@ -42,6 +46,7 @@ class ScriptServer(http.server.SimpleHTTPRequestHandler):
 
         if not args:
             super().do_GET()
+            return
 
         scr = args[0]
 
@@ -78,12 +83,13 @@ def run_script(fn, args):
         code = open_script(fn)
         old_sys_argv, sys.argv = sys.argv, args
         try:
-            exec(code)
+            exec(code, exec_globals, exec_locals)
         except BaseException as e: # need to catch SystemExit etc. as well
             print("_" * 80)
             tn = type(e).__name__
             msg = f"{tn}: {e}"
             print(msg, file=sys.stderr)
+            traceback.print_exc()
         sys.argv = old_sys_argv
     return sio.getvalue()