use Logfile;
use Communication;

$log = new Logfile (...);
$log->open(...);

my $func;
$func=sub{
  $data=shift;
  $log->write($data) if($log->is_open());
}

$com = new Communication ($func, ...);

$log->open(...);
$log->write(...) if($log->is_open());

$com->do_something();

$log->close(...);

....
package Communication;

sub new
{
  my $class=shift;
  my $log=shift;
  $log=sub{} if(!($log and ref($log) eq 'CODE'));
  ....
  $self->{LOG}=$log;
  ....
  bless($self, $class);
  return $self;
}

sub do_something
{
 my $self=shift;
  ....
  $self->{LOG}->(...);
  ....
}
....