ちょっとだけハマったのでメモがてら。

httpd.confの編集

/etc/apache2% diff -u httpd.conf.back httpd.conf                                                                                                                                                                            [19:39:39]
--- httpd.conf.back 2014-10-26 19:38:22.000000000 +0900
+++ httpd.conf  2014-10-26 19:39:14.000000000 +0900
@@ -154,7 +154,7 @@
 LoadModule autoindex_module libexec/apache2/mod_autoindex.so
 #LoadModule asis_module libexec/apache2/mod_asis.so
 #LoadModule info_module libexec/apache2/mod_info.so
-#LoadModule cgi_module libexec/apache2/mod_cgi.so
+LoadModule cgi_module libexec/apache2/mod_cgi.so
 #LoadModule dav_fs_module libexec/apache2/mod_dav_fs.so
 #LoadModule dav_lock_module libexec/apache2/mod_dav_lock.so
 #LoadModule vhost_alias_module libexec/apache2/mod_vhost_alias.so
@@ -416,7 +416,7 @@
     # To use CGI scripts outside of ScriptAliased directories:
     # (You will also need to add "ExecCGI" to the "Options" directive.)
     #
-    #AddHandler cgi-script .cgi
+    AddHandler cgi-script .cgi

     # For type maps (negotiated resources):
     #AddHandler type-map var

変更したらapacheのリスタート。
sudo apachectl restart
これで、/Library/WebServer/CGI-Executables/に配置したcgiの実行が
可能になります。