Perl is a high-level programming language with an eclectic heritage written by Larry Wall. Perl like Javascript is a scripting language which adds interactivity to web site pages. You can find bulletin boards, chat rooms and a wide variety of other web site applications that are written in Perl. Perl derives from the ubiquitous C programming language and to a lesser extent from sed, awk, the Unix shell, and at least a dozen other tools and languages. Perl is great for creating programs for web sites such as,

• system utilities,
• software tools,
• system management tasks,
• database access,
• graphical programming,
• networking, and
• world wide web programming.

Perl builds and runs on a number of platforms,

• Virtually all known and current Unix derivatives are supported (Perl's native platform)
• VMS,
• DOS,
• OS/2,
• Windows,
• QNX,
• BeOS,
• Amiga

Perl FAQ

• How can I compile Perl

  • To compile Perl you need a C compiler on your machine. If your vendor did not include one with your system, then grab a binary version of gcc from the net,

    check,
    

    • http://www.perl.com/pub/language/info/software.html#binary
      
    • http://www.perl.com/CPAN/ports/

    If you are on a UNIX its probably best to compile Perl yourself from the source code distribution. If you are on Windows or MacOS, you will probably be best with a binary build.

• Perl scripting basics

  • If you are looking to understand a perl script, then these are common elements you may find,

    • # - comment and this line wont get executed.
    • $ - indicates that this is a variable
    • & - if a word starts with a & it is a call to a sub-routine
    • < - the file is being opened for a read operation
    • > - the file is being opened for a write operation
    • >> - the file is being opened for an append operation
    • (.) - this puts together two variables
    • @ - if a word start with this character it indicates a single-dimension array
    • % - if a word starting with this character indicates a two-dimensional array.
• Perl versions

  • Version 4

    • was the fourth major release (March 1991)
    • it's stable but,
    • is old, limited, and no longer maintained;
    • its last patch (4.036) was in 1992

    Version 5

    • name for the fifth major release (October 1994)
    • rewrite of the original perl source code from releases 1 through 4
    • has been modularized, object-oriented, tweaked, trimmed, and optimized
    • interface is mostly the same

    Version 6

    • rewrite of the current release of Perl by the Topaz project
    • 100% source-compatibility with previous releases
    • written in nominally portable C++
• Reporting Perl bugs

  • If you are reporting a bug in the perl interpreter or the modules shipped with Perl, email Perl at this address,

    • perlbug@perl.com

    If you are posting a bug with a non-standard port, a binary distribution, or a non-standard module then you will need to check the documentation that came with it to determine the correct place to post bugs.

• How to start a cgi script with Perl interpreter

  • Most web servers require this line at the start of any cgi script that uses a perl interpreter,

    • #!/usr/local/bin/perl (often the Perl 5 location) , or this,
    • #!/usr/bin/perl (often the Perl 4 location)

    If this causes an error then asked your web host for it's perl compiler path details.

• Basic Perl Script

  • To test your ability to store and run a Perl program, enter and execute something like this,

    
    #!/usr/local/bin/perl -w
    if ($#ARGV >= 0) { $who = join(' ', @ARGV); }
    else { $who = 'World'; }
    print "Hello, $who!\n";

    this should print "Hello" on your screen.

• How to make your Perl CGI script more efficient

  • Each time a GCI script runs it will need to be re-compiled by Perl and will often allocate a megabyte or more of system memory, this can be a killer.

    There are two popular ways to avoid this overhead.

    1. One is running the Apache HTTP server with either of the mod_perl or mod_fastcgi plugin modules.
    2. Two running it with the FCGI module (from CPAN) and the mod_fastcgi module (available from http://www.fastcgi.com/) each of your Perl programs becomes a permanent CGI daemon process.

    These solutions can both effect your system and how you write your CGI programs, so investigate how them carefully.