#!/usr/bin/perl

use strict;
use warnings;

my ($w, @w, %w);

while (<DATA>) {
    chomp;
    @w = (0) x 26;
    $w[$_]++ for map -0x61 + ord lc, /[a-z]/ig;
    push @{$w{"@w"}}, $_;
}

print "@$w\n" while (undef, $w) = each %w;

__DATA__
opt
top
pot
pit
stoop
topos



pit
opt top pot
stoop topos