The call was coming from inside the house! That 404 was being printed by my fastcgi script in response to apache's truly brain dead (and obviously undocumented) decision to set $ENV{'SCRIPT_FILENAME'} to 'proxy:fcgi://127.0.0.1:2022/path/to/my/file/index.stml'. To make your fastcgi scripts portable between apache and non-broken web servers do something like $ENV{'SCRIPT_FILENAME'} =~ s/.*2022//; before opening it.