#!/usr/bin/perl
use strict;
use warnings;
use 5.10.0;

# Build a few lists
my @lists;
for my $i (0 .. 1+int(3*rand)) { # several lists to compare
    push @{$lists[$i]}, int 16 * rand for 1 .. 15;
    print "LIST $i: ", join(", ", @{$lists[$i]}), "\n";
}

# Track the items found in each list, including the order in
# which they appear
my %tally;
for my $listnum (0 .. $#lists) {
    # Get a list
    my $list=$lists{$listnum};
    for my $itemnum (0 .. $#$list) {
        # Get next item from the list
        my $item = $$list[$itemnum];
        # Each item slot (value in list) gets an array,
        # where each slot is associated with a list.
        # In that array is an array of indexes into the
        # list where each item is found
        push @{$tally{$item}[$listnum]}, $itemnum;
    }
}

# Show which items were in all lists
my $all = (1<<$bit)-1;
print "There were $bit lists.  Items found:\n";
for my $item (sort  {$a<=>$b} keys %tally) {
    print "Item $item: ";
    if ($tally{$item} == $all) {
        print "in *all* lists\n";
        next;
    }
    my @present;
    for ($bit=0; $bit<@lists; $bit++) {
        push @present, $bit if $tally{$item} & 1<<$bit;
    }
    print "in lists: ", join(", ", @present), "\n";
}