Perl solution for week 137, part 1

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diff --git a/challenge-137/abigail/perl/ch-1.pl b/challenge-137/abigail/perl/ch-1.pl
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+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See ../README.md
+#
+
+#
+# Run as: perl ch-1.pl < input-file
+#
+
+#
+# The Gregorian calender cycles every 400 years. That is, every calender
+# event, or sequence of calender events, repeats after 400 years.
+# (This is because there are 97 leap days in a 400 year period, which
+# means there are 146097 days in such a period, and 146097 days are
+# exactly 20871 weeks).
+#
+
+#
+# In such a 400 year period, there are 71 long years. A long year
+# starts or ends with a Thursday (a non-leap long year starts and
+# ends with with a Thursday, a leap long year either starts with
+# a Wednesday and ends with a Thursday, or starts with a Thursday,
+# and end with a Friday).
+#
+
+# 
+# Now, we could calculate the day of the week of Jan 1 and Dec 31,
+# either using a module or some handrolled calculations, checking
+# whether at least of those days is a Thursday.
+#
+# Or we could just list the 71 years in a 400 year period, and so
+# some trivial arithmetic.
+#
+# Guess which method we're using.
+#
+
+my @long_year_offsets = qw [
+    004     009     015     020     026
+    032     037     043     048     054
+    060     065     071     076     082
+    088     093     099             
+            105     111     116     122
+    128     133     139     144     150
+    156     161     167     172     178
+    184     189     195             
+            201     207     212     218
+    224     229     235     240     246
+    252     257     263     268     274
+    280     285     291     296     
+                    303     308     314
+    320     325     331     336     342
+    348     353     359     364     370
+    376     381     387     392     398
+];
+
+say for grep {1900  <= $_ <= 2100}
+         map {my $fy = $_; map {$_ + $fy} @long_year_offsets} 1600, 2000;