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diff --git a/challenge-199/jo-37/perl/ch-1.pl b/challenge-199/jo-37/perl/ch-1.pl
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+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0 '!float';
+use PDL;
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS if @ARGV < 2;
+usage: $0 [-examples] [-tests] [N1 N2...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N1 N2...
+    list of numbers
+
+EOS
+
+
+### Input and Output
+
+say count_good_2(@ARGV);
+
+
+### Implementation
+
+# This task may be regarded as a simplified variant of challenge 196/1.
+# The first transformation step is from index i to index j > i having
+# the same value.  The second step goes from index j to index k < j
+# having the same value again, where i shall be equal to k.  The
+# possible starting indices then are given by the nonzero elements in
+# the diagonal of the product matrix.  Actually, the diagonal has the
+# number of solutions for every starting index and thus the sum over the
+# diagonal is the requested number of good pairs.
+# See
+# https://github.com/manwar/perlweeklychallenge-club/blob/master/challenge-196/jo-37/perl/ch-1.pl
+# for details.
+
+sub count_good_2 {
+	my $l = long @_;
+    # Matrix indicating pairs of equal values in the list.
+    my $eqt = ($l == $l->dummy(0));
+    # Combining the value transition matrix and the index transition
+    # matrix by invalidating the upper right triangle values (including
+    # the diagonal) utilizing symmetry.
+    $eqt->where($l->sequence >= $l->sequence->dummy(0)) .= 0;
+
+    # Chain the transition matrix with its transposed and sum over the
+    # diagonal.
+    ($eqt->xchg(0, 1) x $eqt)->diagonal(0, 1)->sum;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is count_good_2(1, 2, 3, 1, 1, 3), 4, 'example 1';
+        is count_good_2(1, 2, 3), 0, 'example 2';
+        is count_good_2(1, 1, 1, 1), 6, 'example 3';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+	}
+
+    done_testing;
+    exit;
+}