my %Actions = (
   login => {
      libs => [
         "Sources::Env",
         "Sources::Global",
         "Sources::Authenticate",
      ],
      subs => [
         \&Sources::Env::global_set,
         \&Sources::Global::write_standardhttp_header,
         \&Sources::Authenticate::write_loginmask,
      ],
   },
);

sub handler
{
   my ($obj) = @_;
   my $action = lc($obj->{CGI}->getparam('action')) || 'login';

   unless(exists $Actions{$action}->{subs}) { $action = 'login'; }

   foreach my $lib (@{$Actions{$action}->{libs}})
   {
      require $lib;
   }

   foreach my $proc (@{$Actions{$action}->{subs}})
   {
      unless($proc->($obj))
      {
         # error in sub
         last; # errorhandling
      }
   }
}