Cipher plugin using Atbash (somewhat similar to ROT13)

lib/DDG/Goodie/Atbash.pm

@@ -0,0 +1,45 @@
+package DDG::Goodie::Atbash;
+# ABSTRACT: A simple substitution cipher using a reversed alphabet
+
+use DDG::Goodie;
+
+primary_example_queries 'atbash hello';
+secondary_example_queries 'atbash svool';
+description 'A simple substitution cipher using a reversed alphabet';
+name 'Atbash';
+code_url 'https://github.com/duckduckgo/zeroclickinfo-goodies/blob/master/lib/DDG/Goodie/Atbash.pm';
+category 'transformations';
+topics 'cryptography';
+
+attribution web => ['http://kyokodaniel.com/tech/', 'Daniel Davis'],
+            github => ['https://github.com/tagawa', 'tagawa'],
+            twitter => ['https://twitter.com/ourmaninjapan', 'ourmaninjapan'];
+
+triggers start => 'atbash';
+
+zci is_cached => 1;
+
+handle remainder => sub {
+    if ($_) {
+        my $char;
+        my $result;
+        
+        while (/(.)/g) {
+            if ($1 =~ /([a-z])/) {
+                # Substitute lowercase characters
+                $char = chr(219 - ord $1);
+            }
+            elsif ($1 =~ /([A-Z])/) {
+                # Substitute uppercase characters
+                $char = chr(155 - ord $1);
+            }
+            else { $char = $1; }
+            $result .= $char;
+        }
+        
+        return "Atbash: $result";
+    }
+    return;
+};
+
+1;

t/Atbash.t

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+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use Test::More;
+use DDG::Test::Goodie;
+
+zci answer_type => 'atbash';
+zci is_cached => 1;
+
+ddg_goodie_test(
+        [qw(
+                DDG::Goodie::Atbash
+        )],
+        'atbash test' => test_zci('Atbash: gvhg'),
+        'atbash This is a test' => test_zci('Atbash: Gsrh rh z gvhg'),
+        'atbash Gonna party like it\'s 1999!' => test_zci('Atbash: Tlmmz kzigb orpv rg\'h 1999!'),
+);
+
+done_testing;