>  
>  The following pices of code do not work:
>  
>  -----------------------------------------------------
>  code sample 1
>  --------------
>  
>  1.  sub handler {
>  2.    my $r = instance Apache::Request(shift);
>  3. 
>  4.    $r->dir_config(MyVar => undef);
>  5.   
>  6.    $r->dir_config->unset("MyVar");
>  7.
>  8.    $r->dir_config->set(MyVar => undef);
>  9.
>  10. }
>    
>  
>  None of lines 4, 6 or 8 actually unset the variable. 


did you try $r-> server->dir_config->unset("MyVar") as well?

the dir_config table is a bit strange, since it merges per-server and 
per-directory configurations at runtime - from what I remember when 
playing with this last time, if you remove it from the per-dir config 
but you set it on a per-server config (which sounds like what you are 
doing) it will be perpetually re-populated on access to the per-dir 
config.  so, you may need to wipe both dir_config tables clean in 
order to really unset the variable from your handler.

HTH

--Geoff