#!/usr/bin/env perl

use strict;
use warnings;

my %data = (
    A => [qw{ant bee cat dog eel fly gnu hog}],
    B => [qw{ant cat eel gnu}],
    C => [qw{bee dog fly hog}],
    D => [qw{cat fly ant}],
    E => [qw{ant dog gnu}],
    F => [qw{gnu bee}],
    G => [qw{eel hog}],
    H => [qw{zoo}],
    I => [qw{}],
);

my %temp;

for my $set (keys %data) {
    my @elems = @{$data{$set}};
    @elems = ('') unless @elems;

    for my $elem (@elems) {
        push @{$temp{$elem}}, $set;
    }
}

my (%venn, %seen);

for my $elem (sort keys %temp) {
    my @sets = @{$temp{$elem}};

    my $glob_expr = '{' . join(',', @sets) . '}';

    for my $i (1 .. $#sets) {
        $glob_expr .= '-{,' . join(',', @sets[$i .. $#sets]) . '}';
    }

    for my $key (glob($glob_expr)) {
        next if $key =~ /([^-]+)(?=.*?\1)/;
        $key =~ y/-/-/s;
        $key =~ s/(?:^-|-$)//g;
        $key = join '-', sort split /-/, $key;
        push @{$venn{$key}}, $elem unless $seen{$key}{$elem}++;
    }
}

# DEMO: Output
my $fmt = "%-7s  %s  %s\n";

{
    no warnings 'qw';
    printf $fmt, qw{Sets # Elements};
    printf $fmt, qw{---- - --------};
}

printf $fmt, $_, 0+@{$venn{$_}}, "@{$venn{$_}}" for sort keys %venn;