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diff --git a/challenge-100/dave-jacoby/perl/ch-1.pl b/challenge-100/dave-jacoby/perl/ch-1.pl
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+++ b/challenge-100/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,70 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental::postderef experimental::signatures };
+
+# You are given a time (12 hour / 24 hour).
+#
+# Write a script to convert the given time from 12 hour format to 24 hour format and vice versa.
+#
+# Ideally we expect a one-liner.
+
+my @times =
+    sort { $b =~ /m/ <=> $a =~ /m/ }
+    sort
+
+    (
+    '5:14',  '05:15 pm', '05:15pm', '05:15 am', '05:15am', '17:15',
+    '19:15', '07:15 pm', '07:15pm', '12:00am',  '12:00pm', '00:00',
+    '12:00', '24:00',    '7:7am',   '7:7pm'
+    );
+
+for my $time (@times) {
+    say join "\t", '', $time, ' <=> ', switch_time($time);
+    say '';
+}
+
+# 12pm is noon
+# 12am is midnight
+sub switch_time ( $time ) {
+    my $out = '';
+
+    # 12-hour time
+    if ( $time =~ /m$/mix ) {
+        my ( $hr, $min, $ampm ) = $time =~ /(\d+):(\d+)\s*(am|pm|)/mix;
+        $out = join ':',
+            (
+            $ampm eq 'am'
+            ? ( 
+                $hr == 0 ? '00': $hr 
+                )
+            : (
+                $hr == '12'
+                ? sprintf '%02d',
+                $min
+                : sprintf '%02d',
+                $hr + 12
+            )
+            ),
+            ( sprintf '%02d', $min );
+    }
+
+    # 24-hour time
+    else {
+        my ( $hr, $min ) = $time =~ /(\d+):(\d+)/mix;
+        $out = join '',
+            (
+            $hr == 0 || $hr == 24
+            ? 12
+            : ( $hr > 12 ? $hr % 12 : $hr )
+            ),
+            (':'),
+            ( sprintf '%02d', $min ),
+            ( $hr < 12 ? 'am' : 'pm' );
+    }
+    return $out;
+}
+
+