Finally, whenever you need to access the value entered by the system administrator for a configuration directive, you can do so using some very simple Perl code:

use MT;
sub some_method {
    my ($foo) = @_;
    my $log = MT->config('CustomErrorLog');
    # do stuff
}

Note: One thing of interest is the static reference to MT. MT is actually a singleton and as a result there is no need for a developer to instantiate an instance of MT each an every time they need to access its context.