what is perl

Perl is a programming language which can be used for a large variety of tasks. A typical simple use of Perl would be for extracting information from a text file and printing out a report or for converting a text file into another form. But Perl provides a large number of tools for quite complicated problems, including systems programming.
Programs written in Perl are called Perl scripts, whereas the term the perl program refers to the system program named perl for executing Perl scripts. (What, confused already?)
If you have used shell scripts or awk or sed or similar (Unix) utilities for various purposes, you will find that you can normally use Perl for those and many other purposes, and the code tends to be more compact. And if you haven't used such utilities but have started thinking you might have need for them, then perhaps what you really need to learn is Perl instead of all kinds of futilities.
Perl is implemented as an interpreted (not compiled) language. Thus, the execution of a Perl script tends to use more CPU time than a corresponding C program, for instance. On the other hand, computers tend to get faster and faster, and writing something in Perl instead of C tends to save your time.