1 files changed, 60 insertions, 0 deletions
diff --git a/challenge-121/jo-37/perl/ch-1.pl b/challenge-121/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..be854bb6df
--- /dev/null
+++ b/challenge-121/jo-37/perl/ch-1.pl
@@ -0,0 +1,60 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV == 2;
+usage: $0 [-examples] [-tests] [M N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+M
+    number to be processed
+
+N
+    bit position
+
+EOS
+
+
+### Input and Output
+
+say invert_nth_bit($ARGV[0], $ARGV[1]);
+
+
+### Implementation
+
+sub invert_nth_bit ($m, $n) {
+	$m ^ 1 << ($n - 1);
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is invert_nth_bit(12, 3), 8, 'example 1';
+        is invert_nth_bit(18, 4), 26, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is invert_nth_bit(0, 32), 2 ** 31, 'not limited to N <= 8';
+        is invert_nth_bit(2 ** 31, 32), 0, 'not limited to M < 256';
+	}
+
+    done_testing;
+    exit;
+}