#!/usr/bin/env perl

use strict;
use warnings;

my @strings = qw(AGCT AGGT GG AGCT);

my %uniques;
$uniques{shift @strings}++ while @strings;

my @slots;
while (my $i = each %uniques) {
    push @{$slots[length $i]}, $i;
    delete $uniques{i};
}

my $master = join (':', @{pop @slots});
while (@slots) {
    my @nomatch = grep {index ($master, $_) < 0} @{pop @slots or []};
    $master .= ':' . join (':', @nomatch) if @nomatch;
}
    
# answer
$master =~ s/:/\n/g;
print $master;