CIO — We all know that when faced with a job to do, we usually tend to reach for the most familiar tool in our belt. And while perl is certainly a versatile tool, it isn't the right tool for every job.

Perl is the granddaddy of the open-source scripting languages, with the 1.0 release seeing the light of day way back in 1987. By comparison, PHP wasn't released until 1994, and Python didn't have its 0.9 release until 1991—only the Unix shells themselves have an older pedigree. The O'Reilly "Camel" book (Programming perl) has been a ubiquitous presence on cubicle bookshelves for decades.

Like any language, perl has its strengths and weaknesses. With that in mind, here's some recommended uses and abuses of the elder statesman of scripting.

The Good

1. Pattern matching: Perl's greatest claim to fame has always been the tight integration of regular expressions into the base language syntax. For most developers, perl was the first time they ever used a regular expression.

   As a result, perl has always been the go-to language for any task that involves pattern-matching input. A typical use of this capability is to scan an input stream for name/value pairs and split them. Another is parsing log files with a fixed but variable length format. It's not for nothing that a lot of the popular log file auditing packages are written in perl.

2. In-place editing: Combine regular expressions with the ability to edit files "in place" from the command line, and perl makes a dandy tool for performing a batch modification on a group of files. For example, suppose you have renamed the /home/george directory to /home/curious, and want to update a few hundred scripts in the /usr/lib/yellowhat directory to point at the correct new path. The following one-liner will do just that:

   # perl -i.bak -p -e "s#/home/george#/home/curious#" `find . -print`

   Now, this is a fairly simple example and could have easily been done using a tool such as sed, but the important thing is that you could have used any arbitrarily complex perl program as the filter, and done highly complex manipulations. Imagine an area code getting split and having to replace a single area code with one of two depending on the original exchange in hundreds of files. In perl, it would be a snap.

3. A replacement for shell scripts: One of the worst things about shell scripting—whether in bash, sh or csh—is that the syntax of the scripts themselves is fairly hard to read. By using perl as a scripting language instead of a "traditional" shell, you can use much more C-like syntax without sacrificing functionality.

4. As a database manipulation tool: One of perl's strengths has always been the strong database interoperability through the DBI and DBD libraries. If you need to create a quick database report, or convert between a database and some other form of data storage, you can very easily whip up a little utility using perl in very short time.

5. As a cross-platform language: Because perl is interpreted, perl scripts don't need to be recompiled when moved from platform to platform. And because companies like ActiveState have produced strong ports of perl to platforms such as Windows, most perl programs will run without modification even if they do advanced things such as database connectivity, file system modification or network programming.

Continue Reading