Emacs::Lisp provides support for writing Emacs extensions in Perl.
Emacs allows you to customize your environment using Lisp. With EPL, you can use Perl, too. This module allows Perl code to call functions and access variables of Lisp.
You still need to learn some Lisp in order to understand The Elisp Manual, which is the definitive reference for Emacs programming. This document assumes a basic understanding of Emacs commands and Lisp data types. I also assume familiarity with Perl's complex data structures (described in perlref) and objects (see perlobj).
Perlmacs was (is?) a project that embedded a Perl interpreter into the Emacs binary so that it could run Lisp, Perl, or any combination of the two. It uses Perl's C interface, which requires patching and recompiling Emacs. As a result, each release is tied to a version of Emacs, it takes a lot of time and disk space to build, and it is not very portable.
EPL (Emacs Perl) accomplishes most of what Perlmacs can do, but it does not suffer from the same drawbacks. It uses unmodified Emacs and Perl and lets them work together through IPC (pipes). This may make some tasks much slower, but it is much more convenient to install and upgrade, and it works with XEmacs as well as Emacs 21 betas.