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diff --git a/challenge-162/peter-campbell-smith/blog.txt b/challenge-162/peter-campbell-smith/blog.txt
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+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
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+++ b/challenge-162/peter-campbell-smith/perl/ch-1.pl
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+#!/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 - $sum % 10) . '.';
+}
+
diff --git a/challenge-162/peter-campbell-smith/perl/ch-2.pl b/challenge-162/peter-campbell-smith/perl/ch-2.pl
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+#!/usr/bin/perl
+
+# Peter Campbell Smith - 2022-04-25
+# PWC 162 task 2
+
+use v5.28;
+use strict;
+use warnings;
+use utf8;
+
+my ($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];
+		}
+	}
+}