Challenge 146 task 2

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diff --git a/challenge-146/jo-37/perl/ch-2.pl b/challenge-146/jo-37/perl/ch-2.pl
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+#!/usr/bin/perl -s
+
+use v5.24;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV == 1;
+usage: $0 [-examples] [-tests] [D/N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+D/N
+    fraction
+
+EOS
+
+
+### Input and Output
+
+main: {
+    my @parents;
+    push @parents, curious_parent(split m{/}, shift, 2);
+    push @parents, curious_parent($parents[-1]->@*);
+    local $, = ' ';
+    say map {join '/', @$_} @parents;
+}
+
+
+### Implementation
+
+# The child nodes are made from the parent's
+# - numerator and numerator + denominator
+# - numerator + denominator and denominator
+# In reverse, the parent depends on the order of the child's denominator
+# and numerator and may be reconstructed easily.
+sub curious_parent ($d, $n) {
+    $d < $n ? [$d, $n - $d] : [$d - $n, $n];	
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+        my $parent = curious_parent(3, 5);
+        is $parent, [3, 2], 'example 1 parent';
+        is curious_parent(@$parent), [1, 2], 'example 1 grandparent';
+
+        $parent = curious_parent(4, 3);
+        is $parent, [1, 3], 'example 2 parent';
+        is curious_parent(@$parent), [1, 2], 'example 2 grandparent';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+	}
+
+    done_testing;
+    exit;
+}