Add day 3.

day03.pl

@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+my $sum = 0;
+my $enable = 1;
+
+## Part 1
+#while (<>) {
+#	while (/mul\((\d+),(\d+)\)/g) {
+#		$sum += $1 * $2;
+#	}
+#}
+#print $sum;
+
+## Part 2
+while (<>) {
+	while (/do\(\)|don't\(\)|mul\((\d+),(\d+)\)/g) {
+		if ($& eq 'do()') {
+			$enable = 1;
+			next;
+		} elsif ($& eq "don't()") {
+			$enable = 0;
+			next;
+		}
+
+		$sum += $1 * $2 if ($enable);
+	}
+}
+
+print $sum;