add solution week 82 task 1

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+#!/usr/bin/env perl
+# Week 82 Task 1 solution by Steven Wilson. 
+
+=encoding utf8
+
+=head1 TASK #1 › Common Factors
+Submitted by: Niels van Dijke
+
+You are given 2 positive numbers $M and $N.
+
+Write a script to list all common factors of the given numbers.
+Example 1:
+
+Input:
+    $M = 12
+    $N = 18
+
+Output:
+    (1, 2, 3, 6)
+
+Explanation:
+    Factors of 12: 1, 2, 3, 4, 6
+    Factors of 18: 1, 2, 3, 6, 9
+
+Example 2:
+
+Input:
+    $M = 18
+    $N = 23
+
+Output:
+    (1)
+
+Explanation:
+    Factors of 18: 1, 2, 3, 6, 9
+    Factors of 23: 1
+=cut
+
+use strict;
+use warnings;
+use Test::More;
+use Math::Factor::XS qw/ factors /;
+
+my @e1_t = qw/ 1 2 3 6 /;
+my @e2_t = qw/ 1 /;
+is_deeply( common_factors( 12, 18 ), \@e1_t, 'example 1' );
+is_deeply( common_factors( 18, 23 ), \@e2_t, 'example 2' );
+done_testing();
+
+sub common_factors {
+    my ( $first, $second ) = @_;
+    my %first_factors  = map { $_ => 1 } factors($first);
+    my @second_factors = factors($second);
+    my @intersection   = sort { $a <=> $b }
+        grep { exists $first_factors{$_} } @second_factors;
+    unshift @intersection, 1;
+    return \@intersection;
+}