Added Perl Cheat Sheet (#5035)

free-programming-cheatsheets.md

@@ -15,6 +15,7 @@
 * [Language Translations](#language-translations)
 * [Markdown](#markdown)
 * [MongoDB](#mongodb)
+* [Perl](#Perl)
 * [Python](#python)
 * [Ruby](#ruby)
 * [SQL](#sql)
@@ -102,6 +103,11 @@
 * [Quick Cheat Sheet for Mongo DB Shell commands](https://gist.github.com/michaeltreat/d3bdc989b54cff969df86484e091fd0c) - Michael Treat's Quick Cheat Sheet
 
 
+### Perl
+
+* [Perl Reference card](https://michaelgoerz.net/refcards/perl_refcard.pdf) (PDF)
+
+
 ### Python
 
 * [Comprehensive Python Cheatsheet](https://gto76.github.io/python-cheatsheet) - Jure Šorn (HTML)