PERL - First Script

With PERL installed we are ready to dive into our first script. There are a few elements every PERL script must contain in order to function. Open up your favorite simple text editor, the file extension for PERL scripts is .pl. Save your files with this extension.

The first line of every PERL script is a commented line directed toward the PERL interpreter. This line is generally the same from one instal of PERL to the next, it might look something like this if you were running it on linux:

#!/usr/bin/perl

And on a windows operating system it may resemble:

#!D:\Perl\bin\perl

In this tutorial we will assume you are running on a linux server (the most common web server), but if you are on windows make sure you use the correct path! The comment points to the installation path of Perl, usually /usr/bin/perl. You can locate the directory tree to Perl somewhere in the documentation of your web server, or email your web host and they can specify your Perl installation directory.

Perl - HTTP Headers

Because we are working in a web environment we are sort of jumping ahead of the game. We have to introduce some HTTP headers so that Perl understands we are working with a web browser. To do this we have to run another line of strange code called an HTTP header as you may have guessed. It looks something like this:

#!/usr/bin/perl

print "content-type: text/html \n\n";

At this point our script still has no real functionality, all we have done thus far is locate our PERL interpreter and tell it that we are going to be working with a web browser or in a web environment.

PERL - Hello, Perl! Script

Now that we have located the interpreter and told PERL we are working with the web, we can print text to the browser with the print function.

#!/usr/bin/perl

print "content-type: text/html \n\n";

print "Hello, Perl!";

Display:

You should see "Hello, Perl!" in the top left corner of your browser. If you have a problem, ask about it on the Perl Forum

Perl - Execute Your First Script

Now it is time to upload your firstscript-linux.pl to your web server and execute it. After you upload your file be sure to CHMOD the script file and allow anonymous execution priviledge, generally a setting of 0755 works perfectly.

Your script is working perfectly if you are staring at a blank screen and didn't recieve a 500 or 404 error message.

Perl - Debugging Your Script(s)

If you are using an FTP program to upload your scripts, set the upload type to ASCII or "Text". This setting prevents the mysterious addition of random characters that sometimes happens when copying files across different operating systems. Learning to do this prevents hours of headaches and frustration.

Another great debugging technique is to isolate the code you are currently working on. To do this you can temporarily comment out lines of code to isolate only the section that is returning an error message.

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