Challenge 054 task 2

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diff --git a/challenge-054/jo-37/perl/ch-2.pl b/challenge-054/jo-37/perl/ch-2.pl
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+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use List::Gen;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N
+    print N's Collatz sequence
+
+EOS
+
+
+### Input and Output
+
+# Append the final "one".
+(gen_collatz(shift) + [1])->say;
+
+
+### Implementation
+
+sub gen_collatz ($n) {
+    # Generator for N's Collatz sequence.
+    iterate {$_ % 2 ? $_ * 3 + 1 : $_ / 2}->from($n)->until('== 1');
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is gen_collatz(23)->apply, [23, 70, 35, 106, 53, 160, 80, 40,
+            20, 10, 5, 16, 8, 4, 2], 'example';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+	}
+
+    done_testing;
+    exit;
+}