Complete day 1.

day01.pl

@@ -0,0 +1,32 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+my @list1;
+my @list2;
+
+while (<>) {
+	my @nums = split;
+	next unless @nums;
+	push @list1, $nums[0];
+	push @list2, $nums[1];
+}
+
+@list1 = sort { $a <=> $b } @list1;
+@list2 = sort { $a <=> $b } @list2;
+
+my $elementwise_diff = 0;
+for (my $i = 0; $i < @list1; $i++) {
+	my $diff = abs($list1[$i] - $list2[$i]);
+	$elementwise_diff += $diff;
+}
+
+print $elementwise_diff . "\n";
+
+my $similarity_score = 0;
+for my $element (@list1) {
+	$similarity_score += $element * grep { $_ == $element } @list2;
+}
+
+print $similarity_score . "\n";