sub bind {
  my ($callback, @args) = @_;
  $callback->(@args);	
}

##</code><code>##

bind(\&debug, "Entering xxx()");
...
bind(\&logit, "Username : $user logged in")
... and so on...

##</code><code>##

sub bind {
  my $monad = shift;#self
  my $callback = shift;
  my @args = @_;
  my @res =  $callback->(@args);
  $monad->pack_args(@res);
  return $monad
}

my $monad = new Monad;
$monad->bind(\&debug, "Entering xxx()");
...
$monad->bind(\&logit, "Username : $user logged in")
... and so on...