3 files changed, 83 insertions, 0 deletions
diff --git a/challenge-227/dave-jacoby/blog.txt b/challenge-227/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..0e391a293c
--- /dev/null
+++ b/challenge-227/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2023/07/24/if-sept-seven-why-is-it-the-ninth-month-weekly-challenge-ccxxvii.html
diff --git a/challenge-227/dave-jacoby/perl/ch-1.pl b/challenge-227/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..bf3f29e656
--- /dev/null
+++ b/challenge-227/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,44 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+use DateTime;
+
+my @examples = (
+    1753,
+    1800,
+    1900,
+    2000,
+    2009, 
+    2023,
+    2100,
+    3000,
+    4000,
+    9000,
+    9999
+);
+
+for my $year (@examples) {
+    my $count = find_friday13s($year);
+    say <<~"END";
+    Input:  \$year = $year
+    Output: $count
+    END
+}
+
+sub find_friday13s ($year) {
+    my $count = 0;
+    my @months;
+    for my $month ( 1 .. 12 ) {
+        my $dt = DateTime->now();
+        $dt->set_year($year);
+        $dt->set_day(13);
+        $dt->set_month($month);
+        $count++ if $dt->day_of_week == 5;
+        push @months, $month if $dt->day_of_week == 5;
+
+    }
+    return $count;
+}
diff --git a/challenge-227/dave-jacoby/perl/ch-2.pl b/challenge-227/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..5a1c3617f7
--- /dev/null
+++ b/challenge-227/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,38 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+use Roman;
+
+my @examples = (
+    "IV + V",
+    "M - I",
+    "X / II",
+    "XI * VI",
+    "VII ** III",
+    "V - V",
+    "V / II",
+    "MMM + M",
+    "V - X",
+);
+
+for my $e (@examples) {
+    my $pad = ' ' x (10 - length $e);
+    my $output = roman_maths($e);
+    print <<~"END";
+    $e $pad => $output
+    END
+}
+
+sub roman_maths ($equation) {
+    my ( $first, $expression, $second ) = split /\s+/mx, $equation;
+    my ( $f, $s ) = map { arabic($_) } $first, $second;
+    my $arabic = eval( join ' ', $f, $expression, $s );
+    my $roman = Roman($arabic);
+    $roman = undef if $arabic =~ /\./mx;
+    return $roman if defined $roman && $arabic > 0;
+    return 'nulla' if $arabic == 0;
+    return 'non potest' ;
+}