sub columns {
  my $result;

  # http://search.cpan.org/~kjalb/TermReadKey/ReadKey.pm
  # Term::ReadKey is not a standard Perl module, and may not be installed. If the user resizes the terminal
  # while the program is running, this will correctly reflect the resizing.
  eval 'use Term::ReadKey; my ($wchar, $hchar, $wpixels, $hpixels) = GetTerminalSize(); $result=$wchar';  
     
  # http://search.cpan.org/~nwclark/perl-5.8.8/lib/Term/ReadLine.pm
  # Term::ReadLine is a standard Perl module, but exists in different implementations under the hood. On a Linux
  # system, it's implemented using Term::ReadLine::Gnu, which supports get_screen_size(). On a default FreeBSD system,
  # however, the following won't work; you'd have to install the p5-ReadLine-Gnu package to get support for this function.
  if (!$result) {
    eval 'use Term::ReadLine; $term = new Term::ReadLine("foo"); my ($r,$c)= Term::ReadLine::get_screen_size(); $result=$c';
  }
  return $result;
}