Perl Programming

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.

Origins

Perl began as the result of one man's frustration and, by his own account, inordinate laziness. It is a unique language in ways that cannot be conveyed simply by describing the technical details of the language. Perl is a state of mind as much as a language grammar.

One of the oddities of the language is that its name has been given quite a few definitions. Originally, Perl meant the Practical Extraction Report Language. However, programmers also refer to is as the Pathologically Eclectic Rubbish Lister. Or even, Practically Everything Really Likable.

Let's take a few minutes to look at the external forces which provoked Perl into being-it should give you an insight into the way Perl was meant to be used. Back in 1986, Larry Wall found himself working on a task which involved generating reports from a lot of text files with cross references. Being a UNIX programmer, and because the problem involved manipulating the contents of text files, he started to use awk for the task. But it soon became clear that awk wasn't up to the job; with no other obvious candidate for the job, he'd just have to write some code.

Now here's the interesting bit: Larry could have just written a utility to manage the particular job at hand and gotten on with his life. He could see, though, that it wouldn't be long before he'd have to write another special utility to handle something else which the standard tools couldn't quite hack. (It's possible that he realized that most programmers were always writing special utilities to handle things which the standard tools couldn't quite hack.)

So rather than waste any more of his time, he invented a new language and wrote an interpreter for it. If that seems like a paradox, it isn't really-it's always a bit more of an effort to set yourself up with the right tools, but if you do it right, the effort pays off.

The new language had an emphasis on system management and text handling. After a few revisions, it could handle regular expressions, signals, and network sockets, too. It became known as Perl and quickly became popular with frustrated, lazy UNIX programmers. And the rest of us.

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