use Getopt::Long::Framework;

  Getopt::Long::Framework->accept(
    'qwib=i' => {
      default => 30,
      validate => qr/^(?:\d|\d\d)$/,
      help => 'sets up the qwibble factor',
    },
    'blah|b=s' => {
      default => sub { $ENV{blah} || 'frobnicate' },
      validate => sub { -d $_ },
      help => 'sets the frobnicator directory',
    },
  );

  my $frob_dir = Getopt::Long::Framework->getOpt('blah');