sub log_file {
    my $self = shift;

    return(${*$self}{exp_Log_File})
      if not @_;  # we got no param, return filehandle

    my $file = shift;
    my $mode = shift || "a";

    if (${*$self}{exp_Log_File} and ref(${*$self}{exp_Log_File}) ne 'CODE') {
      close(${*$self}{exp_Log_File});
      ${*$self}{exp_Log_File} = undef;
    }
    return if (not $file);
    my $fh = $file;
    if (not ref($file)) {
      # it's a filename
      $fh = new IO::File $file, $mode
        or croak "Cannot open logfile $file: $!";
    }
    if (ref($file) ne 'CODE') {
      croak "Given logfile doesn't have a 'print' method"
        if not $fh->can("print");
      $fh->autoflush(1);                # so logfile is up to date
    }

    ${*$self}{exp_Log_File} = $fh;
}