This week, after having read the tasks, I decided to demonstrate the power of CPAN. There already are modules that solve the problems, so the only skill you need is the art of searching CPAN.

When I read the definition of an anagram in Wikipedia, I knew I would need a combinatorics module. I first checked Math::Combinatorics and tried to generate all the anagrams using its next_permutation method. I could have used Algorithm::Combinatorics and its permutations, as well.

But there was a catch: if a letter is repeated in the input word, the anagrams won’t be unique. I didn’t want to reach for List::Util’s uniq as it needs to keep all the anagrams in memory while the iterator had much lower memory footprint. Fortunately, I knew that “unique” means “hash” in Perl.

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Math::Combinatorics;

my @letters = split //, shift;
my $iter = 'Math::Combinatorics'->new(data  => \@letters);
my %seen;
$seen{$_}++ or say $_ while $_ = join '', $iter->next_permutation;