If you try to do something only if some include is loaded successfully you may try to do:
if(@include('some/file.inc')) { do_sth(); }
and it will most likely work, but sometimes you want to add extra parameter to this like this:
if(@include('some/file.inc') and $feature_enabled) { do_sth(); }
and in this case it will fail spectacularly. The fix to this is quite simple, but took me lots of time to find:
if((@include('some/file.inc')) and $feature_enabled) { do_sth(); } // Ya, faken (parentheses) ...