Merge branch 'manwar:master' into master

12 files changed, 729 insertions, 0 deletions

diff --git a/challenge-162/dave-jacoby/blog.txt b/challenge-162/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..6d9cddbe8c
--- /dev/null
+++ b/challenge-162/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2022/04/26/play-fair-and-by-the-book-weekly-challenge-162.html
diff --git a/challenge-162/dave-jacoby/perl/ch-1.pl b/challenge-162/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..3c1b975c5b
--- /dev/null
+++ b/challenge-162/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+use List::Util qw{ sum0 };
+
+my @samples;
+push @samples, '978-0-306-40615-7';    # error-correction coding
+                                       # for digital communication
+push @samples, '978-0596001735';       # perl best practices
+push @samples, '978-0596003135';       # perl cookbook
+push @samples, '978-0596004927';       # programming perl
+push @samples, '978-1492094951';       # learning perl
+push @samples, '978-1680500882';       # modern perl
+
+for my $sample (@samples) {
+    my $check = find_check_digit($sample);
+    say <<"END";
+    ISBN-13: $sample
+    Check:   $check
+END
+}
+
+sub find_check_digit( $isbn13) {
+    my @digits = $isbn13 =~ /(\d)/gmix;
+    pop @digits;
+    push @digits, 0;
+    my @x = map { $_ % 2 == 1 ? 3 * $digits[$_] : $digits[$_] } 0 .. 12;
+    return 10 - ( ( sum0 @x ) % 10 );
+}
diff --git a/challenge-162/dave-jacoby/perl/ch-2.pl b/challenge-162/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..f229c6b940
--- /dev/null
+++ b/challenge-162/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,131 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+use JSON;
+my $json = JSON->new->canonical;
+
+my @tests;
+push @tests,
+    [
+    'playfair example',
+    'hide the gold in the tree stump',
+    'bmodzbxdnabekudmuixmmouvif'
+    ];
+push @tests,
+    [ 'perl and raku', 'the weekly challenge', 'siderwrdulfipaarkcrw' ];
+
+for my $test (@tests) {
+    my ( $key, $plain, $cypher ) = $test->@*;
+    my @square = make_playfair_square($key);
+    my $c1     = encrypt( $key, $plain );
+    my $p1     = decrypt( $key, $cypher );
+    say join "\n\t", $key, $plain, $c1, $cypher, $p1,
+        $cypher eq $c1 ? 'true' : 'false';
+    say '';
+}
+exit;
+
+sub encrypt ( $key, $plaintext ) {
+    my @square = make_playfair_square($key);
+    my @input  = make_digrams($plaintext);
+    my @output;
+    for my $digram (@input) {
+        my ( $m,  $n )  = split //, $digram;
+        my ( $mx, $my ) = find_position( $m, @square );
+        my ( $nx, $ny ) = find_position( $n, @square );
+        if    (0) { 'NO-OP' }
+        elsif ( $mx == $nx ) {
+            my $mm = $square[$mx][ ( $my + 1 ) % 5 ];
+            my $nn = $square[$nx][ ( $ny + 1 ) % 5 ];
+            push @output, $mm . $nn;
+        }
+        elsif ( $my == $ny ) {
+            my $mm = $square[ ( $mx + 1 ) % 5 ][$my];
+            my $nn = $square[ ( $nx + 1 ) % 5 ][$ny];
+            push @output, $mm . $nn;
+        }
+        else {
+            my $mm = $square[$mx][$ny];
+            my $nn = $square[$nx][$my];
+            push @output, $mm . $nn;
+        }
+    }
+    my $zed = '';
+    return lc join '', @output;
+}
+
+sub decrypt ( $key, $cyphertext ) {
+    my @square = make_playfair_square($key);
+    my @input  = make_digrams($cyphertext);
+    my @output;
+    for my $digram (@input) {
+        my ( $m,  $n )  = split //, $digram;
+        my ( $mx, $my ) = find_position( $m, @square );
+        my ( $nx, $ny ) = find_position( $n, @square );
+        if    (0) { 'NO-OP' }
+        elsif ( $mx == $nx ) {
+            my $mm = $square[$mx][ ( $my + 4 ) % 5 ];
+            my $nn = $square[$nx][ ( $ny + 4 ) % 5 ];
+            push @output, $mm . $nn;
+        }
+        elsif ( $my == $ny ) {
+            my $mm = $square[ ( $mx + 4 ) % 5 ][$my];
+            my $nn = $square[ ( $nx + 4 ) % 5 ][$ny];
+            push @output, $mm . $nn;
+        }
+        else {
+            my $mm = $square[$mx][$ny];
+            my $nn = $square[$nx][$my];
+            push @output, $mm . $nn;
+        }
+    }
+    my $zed = '';
+    return lc join '', @output;
+}
+
+sub make_playfair_square( $key ) {
+    my %h;
+    my @array = grep { !$h{$_}++ } grep { /\w/ } ( split //, lc $key ),
+        'a' .. 'i', 'k' .. 'z';
+    @array = @array[ 0 .. 24 ];
+    my @square;
+    for my $i ( 0 .. 24 ) {
+        my $x = $i % 5;
+        my $y = int $i / 5;
+        $square[$y][$x] = uc $array[$i];
+    }
+    return @square;
+}
+
+sub make_digrams ( $text ) {
+    my @digrams;
+    my $pt = $text;
+    $pt =~ s/[jJ]/i/gmix;
+    $pt =~ s/[^A-Za-z]+//gmix;
+    while ($pt) {
+        my $digram = substr( $pt, 0, 2 );
+        if ( substr( $digram, 0, 1 ) eq substr( $digram, 1, 1, ) ) {
+            $digram = substr( $pt, 0, 1 ) . 'X';
+            substr( $pt, 0, 1 ) = '';
+        }
+        else { substr( $pt, 0, 2 ) = ''; }
+        $digram .= 'X' unless length $digram == 2;
+        push @digrams, uc $digram;
+    }
+    return @digrams;
+}
+
+sub find_position ( $letter, @square ) {
+    exit unless $letter =~ /[A-Z]/mix;
+    $letter = uc $letter;
+    for my $x ( 0 .. 4 ) {
+        for my $y ( 0 .. 4 ) {
+            my $s = $square[$x][$y] || '-';
+            return ( $x, $y ) if $letter eq $s;
+        }
+    }
+    return ( -1, -1 );
+}
diff --git a/challenge-162/julien-fiegehenn/perl/ch-1.pl b/challenge-162/julien-fiegehenn/perl/ch-1.pl
new file mode 100644
index 0000000000..615f3f75c2
--- /dev/null
+++ b/challenge-162/julien-fiegehenn/perl/ch-1.pl
@@ -0,0 +1,46 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use feature 'say';
+use List::Util 'sum';
+
+# Write a script to generate the check digit of given ISBN-13 code. Please refer wikipedia for more information.
+
+# Example
+# ISBN-13 check digit for '978-0-306-40615-7' is 7.
+
+# https://en.wikipedia.org/wiki/ISBN#ISBN-13_check_digit_calculation
+
+sub isbn_13 {
+    my $number = shift;
+
+    die 'Input required' unless $number;
+
+    # clean up the number
+    $number =~ s/\D//g;
+
+    # we need to do maths on each digit
+    my @digits = split //, $number;
+
+    # discard the check digit
+    pop @digits if @digits == 13;
+
+    # do we have the right amount of digits?
+    die 'This does not look like an ISBN-13' unless @digits == 12;
+
+    # tripple all the even digits
+    $_ *= 3 for @digits[1, 3, 5, 7, 9, 11];
+
+    # and do the maths
+    return 10 - sum(@digits) % 10;
+}
+
+say isbn_13(shift);
+
+__END__
+use Test::More;
+
+is isbn_13('978-0-306-40615-7'), 7;
+
+done_testing;
\ No newline at end of file
diff --git a/challenge-162/julien-fiegehenn/perl/ch-2.pl b/challenge-162/julien-fiegehenn/perl/ch-2.pl
new file mode 100644
index 0000000000..ee3dc3206f
--- /dev/null
+++ b/challenge-162/julien-fiegehenn/perl/ch-2.pl
@@ -0,0 +1,199 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use feature 'say';
+
+use constant {ROW => 0, COL => 1};
+
+# Implement encryption and decryption using the Wheatstone-Playfair cipher.
+#
+# Examples:
+#  (These combine I and J, and use X as padding.)
+#
+#  encrypt("playfair example", "hide the gold in the tree stump") = "bmodzbxdnabekudmuixmmouvif"
+#
+#  decrypt("perl and raku", "siderwrdulfipaarkcrw") = "thewexeklychallengex"
+
+# Comments based on example in  https://de.wikipedia.org/wiki/Playfair.
+
+# Turn on debugging with the DEBUG=0 environment variable.
+
+say encrypt('playfaire example', 'hide the gold in the tree stump');
+say decrypt("perl and raku", "siderwrdulfipaarkcrw");
+
+sub debug($) {
+  print @_ if $ENV{DEBUG};
+}
+
+sub generate_table {
+  my $key = shift;
+
+  my @letters = grep /[A-IK-Z]/, split //, uc $key;
+  push @letters, 'A' .. 'I', 'K' .. 'Z';
+
+  my ($table, $seen);
+
+  for my $row (0 .. 4) {
+    for my $col (0 .. 4) {
+      while (@letters) {
+        my $letter = shift @letters;
+
+        # skip the ones we've seen
+        redo if $seen->{$letter};
+
+        $table->[$row]->[$col] = $letter;
+        $seen->{$letter} = [$row, $col];
+        last;
+      }
+      debug "$table->[$row]->[$col] ";
+    }
+    debug "\n";
+  }
+  debug "\n";
+
+  return ($table, $seen);
+}
+
+sub encrypt {
+  my ($key, $string) = @_;
+
+  my ($table, $lookup) = generate_table($key);
+
+  my $encrypted = q{};
+
+  my @letters = grep /[A-Z]/, split //, uc $string;
+  while (my ($first, $second) = splice @letters, 0, 2) {
+
+    # pad to create a pair if we only have one letter left
+    $second ||= 'X';
+
+    # handle repeated letters
+    if ($first eq $second) {
+      unshift @letters, $second;
+      $second = 'X';
+    }
+
+    debug "$first$second ";
+
+    # 1. The pair HI forms a rectangle, replace it with BM
+    if ( $lookup->{$first}->[ROW] != $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] != $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[$lookup->{$first}->[ROW]]->[$lookup->{$second}->[COL]],
+        $table->[$lookup->{$second}->[ROW]]->[$lookup->{$first}->[COL]],
+      );
+    }
+
+    # 2. The pair DE is in a column, replace it with OD
+    elsif ($lookup->{$first}->[ROW] != $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] == $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[wrap_number($lookup->{$first}->[ROW] + 1)]
+          ->[$lookup->{$first}->[COL]],
+        $table->[wrap_number($lookup->{$second}->[ROW] + 1)]
+          ->[$lookup->{$second}->[COL]],
+      );
+    }
+
+    # 10. The pair EX (X inserted to split EE) is in a row, replace it with XM
+    elsif ($lookup->{$first}->[ROW] == $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] != $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[$lookup->{$first}->[ROW]]
+          ->[wrap_number($lookup->{$first}->[COL] + 1)],
+        $table->[$lookup->{$second}->[ROW]]
+          ->[wrap_number($lookup->{$second}->[COL] + 1)],
+      );
+    }
+    debug " -> $first$second\n";
+
+    $encrypted .= $first . $second;
+  }
+  debug "\n";
+
+  return $encrypted;
+}
+
+sub decrypt {
+  my ($key, $string) = @_;
+
+  my ($table, $lookup) = generate_table($key);
+
+  my $encrypted = q{};
+
+  my @letters = grep /[A-Z]/, split //, uc $string;
+  while (my ($first, $second) = splice @letters, 0, 2) {
+
+    # pad to create a pair if we only have one letter left
+    $second ||= 'X';
+
+    # handle repeated letters
+    if ($first eq $second) {
+      unshift @letters, $second;
+      $second = 'X';
+    }
+
+    debug "$first$second ";
+
+    # 1. The pair HI forms a rectangle, replace it with BM
+    if ( $lookup->{$first}->[ROW] != $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] != $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[$lookup->{$first}->[ROW]]->[$lookup->{$second}->[COL]],
+        $table->[$lookup->{$second}->[ROW]]->[$lookup->{$first}->[COL]],
+      );
+    }
+
+    # 2. The pair DE is in a column, replace it with OD
+    elsif ($lookup->{$first}->[ROW] != $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] == $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[wrap_number($lookup->{$first}->[ROW] - 1)]
+          ->[$lookup->{$first}->[COL]],
+        $table->[wrap_number($lookup->{$second}->[ROW] - 1)]
+          ->[$lookup->{$second}->[COL]],
+      );
+    }
+
+    # 10. The pair EX (X inserted to split EE) is in a row, replace it with XM
+    elsif ($lookup->{$first}->[ROW] == $lookup->{$second}->[ROW]
+      && $lookup->{$first}->[COL] != $lookup->{$second}->[COL])
+    {
+      ($first, $second) = (
+        $table->[$lookup->{$first}->[ROW]]
+          ->[wrap_number($lookup->{$first}->[COL] - 1)],
+        $table->[$lookup->{$second}->[ROW]]
+          ->[wrap_number($lookup->{$second}->[COL] - 1)],
+      );
+    }
+    debug " -> $first$second\n";
+
+    $encrypted .= $first . $second;
+  }
+  debug "\n";
+
+  return $encrypted;
+}
+
+sub wrap_number {
+  my $number = shift;
+
+  return 4 - $number if $number > 4;
+  return $number;
+}
+
+__END__
+
+use Test::More;
+
+is lc encrypt("playfair example", "hide the gold in the tree stump"),
+  "bmodzbxdnabekudmuixmmouvif";
+is lc decrypt("perl and raku", "siderwrdulfipaarkcrw"), "thewexeklychallengex";
+
+done_testing;
\ No newline at end of file
diff --git a/challenge-162/luca-ferrari/raku/ch-1.p6 b/challenge-162/luca-ferrari/raku/ch-1.p6
new file mode 100755
index 0000000000..0c4ccef759
--- /dev/null
+++ b/challenge-162/luca-ferrari/raku/ch-1.p6
@@ -0,0 +1,6 @@
+#!raku
+
+sub MAIN( Str $isbn where { $isbn.chars == 12 && $isbn.comb.grep( * ~~ / <[0 .. 9]> / ).elems == $isbn.chars } ) {
+    my $position = 0;
+    say 10 - ( $isbn.comb.map( { $_ * ( ++$position %% 2 ?? 3 !! 1 ) } ).sum % 10 );
+}
diff --git a/challenge-162/luca-ferrari/raku/ch-2.p6 b/challenge-162/luca-ferrari/raku/ch-2.p6
new file mode 100755
index 0000000000..d3e3e6e2fe
--- /dev/null
+++ b/challenge-162/luca-ferrari/raku/ch-2.p6
@@ -0,0 +1,96 @@
+#!raku
+
+sub build-grid( Str $passprhase ) {
+    my @grid;
+    my $counter = 0;
+    for $passprhase.comb {
+        # skip existing letters
+        next if @grid.grep( $_ );
+        next if $_ !~~ / <[ a .. z ]> /;
+
+        # insert this letter
+        @grid.push: $_;
+        @grid.push: '|' if ++$counter %% 5;
+    }
+
+    # add the other letters
+    unless ( @grid.grep( '|' ).elems == 5 ) {
+        for 'a' .. 'z' {
+            next if @grid.grep( $_ );
+            next if $_ ~~ / i /;
+            next if $_ ~~ / j /;
+
+            # insert this letter
+            @grid.push: $_;
+            @grid.push: '|' if ++$counter %% 5;
+            last if @grid.grep( '|' ).elems == 5;
+        }
+    }
+
+    # now split the array into a matrix
+    my @matrix;
+    for @grid.join.split( '|' ) {
+        next if ! $_;
+        @matrix.push: [ $_.comb ];
+    }
+
+    say @matrix;
+    return @matrix;
+}
+
+
+sub build-pairs( Str $needle ) {
+
+    my @mangled;
+    my @current;
+    for $needle.comb {
+        next if $_ ~~ / ' ' /;
+
+        @current.push: $_  if ! @mangled.grep( $_ );
+        @current.push: 'X' if   @mangled.grep( $_ );
+
+        if @current.elems == 2 {
+            @mangled.push: [@current];
+            @current = ();
+        }
+    }
+
+    return @mangled;
+}
+
+
+sub MAIN() {
+    my @key-matrix = build-grid( 'playfair example' );
+    my @pairs = build-pairs( 'hide the gold in the tree stump' );
+
+
+    for @pairs -> @current-pair {
+        my @rectangle;
+
+        for 0 ..^ @current-pair {
+            my $current_letter = @current-pair[ $_ ];
+            my $found = False;
+
+            for 0 ..^ @key-matrix.elems -> $row {
+                for 0 ..^ 5 -> $column {
+                    if @key-matrix[ $row ][ $column ] ~~ $current_letter {
+                        # found!
+                        @rectangle.push: ( row => $row, col => $column ).Hash;
+                        $found = True;
+                    }
+
+                    last if $found;
+                }
+
+                last if $found;
+            }
+        }
+
+        say @current-pair.join;
+        say @rectangle;
+
+        say @rectangle[ 0 ].^name;
+#        my $is-rectangle = @rectangle[ 0 ]{ row } != @rectangle[ 1 ]{ row } && @rectangle[ 0 ]{ col } != @rectangle[ 1 ]{ col };
+#       say "rettangolo $is-rectangle";
+    }
+}
diff --git a/challenge-162/peter-campbell-smith/blog.txt b/challenge-162/peter-campbell-smith/blog.txt
new file mode 100644
index 0000000000..c35d02e319
--- /dev/null
+++ b/challenge-162/peter-campbell-smith/blog.txt
@@ -0,0 +1 @@
+https://pjcs-pwc.blogspot.com/2022/04/checksums-and-early-encryption.html
diff --git a/challenge-162/peter-campbell-smith/perl/ch-1.pl b/challenge-162/peter-campbell-smith/perl/ch-1.pl
new file mode 100755
index 0000000000..4462e8d091
--- /dev/null
+++ b/challenge-162/peter-campbell-smith/perl/ch-1.pl
@@ -0,0 +1,34 @@
+#!/usr/bin/perl
+
+# Peter Campbell Smith - 2022-04-25
+# PWC 162 task 1
+
+use v5.28;
+use strict;
+use warnings;
+use utf8;
+
+# Write a script to generate the check digit of given ISBN-13 code.
+
+my ($sum, $test, @digits, @multipliers, @tests);
+
+# data
+@tests = ('978-0-306-40615-7', '978-1-85345-445-5', '978-3-468-98143-2');
+
+# multipliers of successive digits as defined
+@multipliers = qw(1 3 1 3 1 3 1 3 1 3 1 3);
+
+for $test (@tests) {
+	
+	# eliminate non-digits
+	@digits = ();
+	push @digits, $1 while $test =~ m|(\d)|g;
+	
+	# create weighted sum of first 12 digits
+	$sum = 0;
+	$sum += $digits[$_] * $multipliers[$_] for (0 .. 11);
+	
+	# and the 13th digit is 10 minus the sum, mod 10
+	say qq[ISBN-13 check digit for '$test' is ] . (10 - $sum % 10) . '.';
+}
+
diff --git a/challenge-162/peter-campbell-smith/perl/ch-2.pl b/challenge-162/peter-campbell-smith/perl/ch-2.pl
new file mode 100755
index 0000000000..990cb22b44
--- /dev/null
+++ b/challenge-162/peter-campbell-smith/perl/ch-2.pl
@@ -0,0 +1,133 @@
+#!/usr/bin/perl
+
+# Peter Campbell Smith - 2022-04-25
+# PWC 162 task 2
+
+use v5.28;
+use strict;
+use warnings;
+use utf8;
+
+my ($c, $j, $key, $letter, $matrix, $r, %used, @key, @letters, @plain,
+	$plain, $fixed, $prev, %locate, $encrypted, $decrypted);
+
+# Implement encryption and decryption using the Wheatstone-Playfair cipher.
+
+# data
+$key[0]   = 'playfair example';
+$plain[0] = 'hide the gold in the tree stump';
+
+$key[1]   = 'Perl and Raku';
+$plain[1] = 'The Weekly Challenge';
+
+$key[2]   = 'the quick brown fox jumps over the lazy dog';
+$plain[2] = q[The curfew tolls the knell of parting day, the lowing herd winds slowly o'er the lea];
+
+# loop over key/plaintext pairs
+for ($j = 0; $key[$j]; $j ++) {
+	
+	# create matrix
+	say qq[\nPlaintext: $plain[$j]\nKey: $key[$j]];
+	$key = lc($key[$j]);
+	$key =~ s|[^a-z]||g;
+	@letters = split(//, $key);
+	
+	# put the unique letters of the key into successive cells of the matrix
+	($r, $c) = (0, 0);
+	%used = ();
+	for $letter (@letters) {
+		$letter = 'i' if $letter eq 'j';
+		next if $used{$letter};   # seen this letter already
+		$used{$letter} = 1;
+		$$matrix[$r][$c] = $letter;
+		$locate{$letter} = [$r, $c];   # row and column containing $letter
+		$c ++;
+		if ($c == 5) {  # reached the end of a row
+			$c = 0;
+			$r ++;
+		}
+	}
+	
+	# now add the rest of the alphabet
+	for $letter ('a' .. 'z') {
+		$letter = 'i' if $letter eq 'j';
+		next if $used{$letter};
+		$used{$letter} = 1;
+		$$matrix[$r][$c] = $letter;
+		$locate{$letter} = [$r, $c];
+		$c ++;
+		if ($c == 5) {
+			$c = 0;
+			$r ++;
+		}
+	}
+	
+	# show matrix
+	say qq[Matrix:];
+	for $r (0..4) {
+		for $c (0..4) {
+			print $$matrix[$r][$c] . ' ';
+		}
+		say '';
+	}
+	
+	# encrypt the plaintext
+	$plain = lc($plain[$j]);
+	$plain =~ s|[^a-z]||g;
+
+	# insert 'x' to split paired letters
+	$fixed = $prev = '';
+	while ($plain =~ m|(.)|g) {
+		$fixed .= 'x' if ($1 eq $prev and length($fixed) % 2 == 1);
+		$fixed .= $1;
+		$prev = $1;
+	}
+	
+	# suffix 'x' if text has odd length
+	$fixed .= 'x' if (length($fixed) % 2 == 1);
+	
+	# encrypt text 2 letters at a time
+	$encrypted = '';
+	while ($fixed =~ m|(.)(.)|g) {
+		$encrypted .= playfair(1, $1, $2);
+	}
+	say qq[Encrypted: $encrypted];
+	
+	# and decrypt it
+	$decrypted = '';
+	while ($encrypted =~ m|(.)(.)|g) {
+		$decrypted .= playfair(0, $1, $2);
+	}
+	say qq[Decrypted: $decrypted];	
+}
+
+sub playfair {   # (encrypt, letter1, letter2)
+	
+	my ($encrypt, $g1, $g2) = @_;
+	my ($g1_row, $g1_col, $g2_row, $g2_col);
+	
+	# get the row and column coordinates of each letter
+	($g1_row, $g1_col) = @{$locate{$g1}};
+	($g2_row, $g2_col) = @{$locate{$g2}};
+	
+	# the letter pair defines a rectangle - swap their columns
+	if ($g1_row != $g2_row && $g1_col != $g2_col) {
+		return $$matrix[$g1_row][$g2_col] . $$matrix[$g2_row][$g1_col];
+		
+	# pair in same column - shift down to encrypt, up to decrypt
+	} elsif ($g1_col == $g2_col) {
+		if ($encrypt) {
+			return $$matrix[($g1_row + 1) % 5][$g1_col] . $$matrix[($g2_row + 1) % 5][$g2_col];
+		} else { # decrypt
+			return $$matrix[($g1_row + 4) % 5][$g1_col] . $$matrix[($g2_row + 4) % 5][$g2_col];
+		}
+		
+	# pair in same row - shift right to encrypt, left to decrypt
+	} elsif ($g1_row == $g2_row) {
+		if ($encrypt) {
+			return $$matrix[$g1_row][($g1_col + 1) % 5] . $$matrix[$g2_row][($g2_col + 1) % 5];
+		} else { # decrypt
+			return $$matrix[$g1_row,][($g1_col + 4) % 5] . $$matrix[$g2_row][($g2_col + 4) % 5];
+		}
+	}
+}
diff --git a/challenge-162/robert-dicicco/perl/ch-1.pl b/challenge-162/robert-dicicco/perl/ch-1.pl
new file mode 100644
index 0000000000..1cf0ee35fe
--- /dev/null
+++ b/challenge-162/robert-dicicco/perl/ch-1.pl
@@ -0,0 +1,28 @@
+#!perl.exe
+
+use strict;
+use warnings;
+use feature qw/say/;
+
+# AUTHOR: Robert DiCicco
+# DATE: 25-APR-2022
+# Challenge 162 ISBN-13 ( Perl )
+
+sub makeCheckDigit {
+  my $n = shift;
+
+  my @arr = split(//,$n);
+  my $evensum = $arr[0] + $arr[2] + $arr[4] + $arr[6] + $arr[8] + $arr[10];
+  my $oddsum = ($arr[1] + $arr[3] + $arr[5] + $arr[7] + $arr[9] + $arr[11]) * 3;
+  my $presum = ($evensum + $oddsum) % 10;
+  my $checkdigit = 10 - $presum;
+
+  return $checkdigit;
+}
+
+my $isbn = '978-0-306-40615-7';
+my $num = substr($isbn,0,15);
+$num =~ tr/\-//d;
+my $checkdigit = makeCheckDigit($num);
+
+say "ISBN-13 check digit for $isbn is $checkdigit.";
diff --git a/challenge-162/robert-dicicco/raku/ch-1.raku b/challenge-162/robert-dicicco/raku/ch-1.raku
new file mode 100644
index 0000000000..f45b241954
--- /dev/null
+++ b/challenge-162/robert-dicicco/raku/ch-1.raku
@@ -0,0 +1,22 @@
+use v6;
+
+# AUTHOR: Robert DiCicco
+# DATE: 26-APR-2022
+# Challenge 162 ISBN-13 ( Raku )
+
+sub makeCheckDigit ( $n) {
+  my @arr = $n.comb;
+  my $evensum = @arr[0] + @arr[2] + @arr[4] + @arr[6] + @arr[8] + @arr[10];
+  my $oddsum = (@arr[1] + @arr[3] + @arr[5] + @arr[7] + @arr[9] + @arr[11]) * 3;
+  my $presum = ($evensum + $oddsum) % 10;
+  my $checkdigit = 10 - $presum;
+
+  return $checkdigit;
+}
+
+my $isbn = '978-0-306-40615-7';
+my $num = substr($isbn,0,15);
+$num ~~ tr/-//;
+my $checkdigit = makeCheckDigit($num);
+
+say "ISBN-13 check digit for $isbn is $checkdigit.";