To start with Perl you need the Perl interpreter. On any UNIX machine there is a 99.99-percent probability that it's already there. On a Windows machine or a Mac, you need to download the latest release of the language and install it on your machine. (See the links at the end of this article for more information.) Perl is widely available on the Web and is free.
Next, make sure you look in the DOCS directory that comes with Perl -- there will be user-manual-type stuff in there. At some point, it would not hurt to read through all of the documentation, or at least scan it. Initially it will be cumbersome, but after reading this article it will make much more sense.