my $col_width = ( sort { $b <=> $a } map { length } ( #sort lengths
                       (keys %lists, map { @$_ } values %lists)                 
                  ) )[0] + 2; #2 is the padding

##</code><code>##

    my %lists;
    my @amazon = qw(hot tropical humid wet);
    my @sahara = qw(hot hot tropical big);

    $lists{"The Amazon is"} = \@amazon;
    $lists{"The Sahara is"} = \@sahara;