sub getline {
  my $self = shift;
  my $line = $self->SUPER::getline() || return undef;
  
  #the _parse function check if the line is well formed and
  #returns a hash references filled with informations from 
  #the line. _parse() returns undef if there is a format
  #error in the line
  my $result = _parse($line);
  if (defined $result) {
    return $result;
  }
  else {
    #this is the tricky part...
    #what should I do?
  }
}