1 files changed, 108 insertions, 0 deletions
diff --git a/challenge-331/jo-37/perl/ch-2.pl b/challenge-331/jo-37/perl/ch-2.pl
new file mode 100755
index 0000000000..24f43eaf2c
--- /dev/null
+++ b/challenge-331/jo-37/perl/ch-2.pl
@@ -0,0 +1,108 @@
+#!/usr/bin/perl
+
+use v5.26;
+use Test2::V0 qw(!float -no_srand);
+use Test2::Tools::Subtest 'subtest_streamed';
+use Getopt::Long;
+use experimental 'signatures';
+
+use PDL v2.100;
+use PDL::NiceSlice;
+
+### Options and Arguments
+
+my ($tests, $examples, $verbose);
+GetOptions(
+    'examples!' => \$examples,
+    'tests!'    => \$tests,
+    'verbose!'  => \$verbose,
+) or usage();
+
+run_tests($examples, $tests);	# tests do not return
+
+usage() unless @ARGV == 2;
+
+sub usage {
+    die <<~EOS;
+    $0 - buddy strings
+
+    usage: $0 [-examples] [-tests] [SOURCE TARGET]
+
+    -examples
+        run the examples from the challenge
+     
+    -tests
+        run some tests
+
+    SOURCE TARGET
+        two strings
+
+    EOS
+}
+
+
+### Input and Output
+
+say +(qw(true false))[!buddy_strings(@ARGV)];
+
+
+### Implementation
+#
+# For details see:
+# https://github.sommrey.de/the-bears-den/2025/07/25/ch-331.html#task-2
+
+
+sub buddy_strings {
+    my $s = long map [map ord, split //], @_;
+    my $diff = which $s->xchg(0, 1)->bxorover;
+
+    $diff->isempty && $s(,0)->uniq->dim(0) < $s->dim(0) ||
+    $diff->nelem == 2 && all $s($diff,0) == $s($diff(-1:0),1);
+}
+
+
+### Examples and Tests
+
+sub run_tests ($examples, $tests) {
+    return unless $examples || $tests;
+
+    state sub run_example ($args, $expected, $name) {
+        my $result = buddy_strings(@$args);
+        is $result, $expected,
+            "$name: (@$args) -> " . $expected->name;
+    }
+
+    plan 2;
+
+    $examples ? subtest_streamed(examples => sub {
+        my @examples = (
+            [["fuck", "fcuk"], T(), 'example 1'],
+            [["love", "love"], F(), 'example 2'],
+            [["fodo", "food"], T(), 'example 3'],
+            [["feed", "feed"], T(), 'example 4'],
+        );
+        plan scalar @examples;
+        for (@examples) {
+            run_example @$_;
+        }
+    }) : pass 'skip examples';
+
+    $tests ? subtest_streamed(tests => sub {
+        my @tests = (
+            [["this", "thus"], F(), 'one different char'],
+            [["this", "then"], F(), 'two different chars'],
+            [["the", "thee"], F(), 'different lengths'],
+            [["seprű", "sűpre"], T(), 'beyond U+00FF'],
+            [["hour", "ouhr"], F(), 'rotated'],
+            [["hour", "ohru"], F(), 'two flips'],
+            [["aaa", "aaa"], T(), 'more non-unique chars'],
+
+        );
+        plan scalar @tests;
+        for (@tests) {
+            run_example @$_;
+        }
+    }) : pass 'skip tests';
+
+    exit;
+}