Discus is written in the Perl programming language, and a properly functioning Perl interpreter must be installed on your system in order for Discus to run properly. Fortunately, an interpreter for the Perl language is available free of charge for nearly every platform imaginable (including unix, Windows, and even Macintosh). Perl is the language of choice for CGI applications and it is installed standard by nearly every web host.

DiscusWare originally developed Discus on Perl 4, but soon after, we switched to Perl 5 after noting better performance. It is now believed that Discus is completely incompatible with Perl 4. Fortunately, most web hosts have finally switched to offering only Perl 5.

Current and future versions of Discus are developed on version 5.6.0 of Perl and back-tested on version 5.005 of Perl. Therefore, DiscusWare makes Perl 5.005 or higher a system requirement. If your web host has upgraded their Perl distribution anytime within the last six years, your Perl distribution will be 5.005 or higher and therefore meet our system requirements!

Version 4 of Perl was released and updated in the years 1991-1993. Version 5.000 of Perl was first introduced in October of 1994 and was essentially a rewrite of the entire language interpreter. The following table notes the dates of the releases of Perl version 5 (from the "perlhist" manpage):

The Discus system requirements state that you must be running version 5.005 or higher of Perl in order to properly run Discus. We have reason to believe that Discus will function quite adequately on some earlier versions of Perl, but we cannot support this.

If you need to download the latest version of Perl, please use the following links to do so:

• CPAN: Binary distributions of Perl for nearly every imaginable platform.

• ActivePerl: Perl distribution for Windows, linux, and solaris.

If your web host is unable or unwilling to upgrade their distribution of Perl to something more than a few years old, you should strongly consider whether or not this web host is doing a good job of maintaining their servers and systems.

If Discus functions properly on your server without errors, then you do not need to be significantly concerned about the old Perl version. We know of many people who have run Discus and Discus Pro successfully on the earliest versions of Perl 5.

You may find, however, that future versions of the Discus software depend on features or modules installed by default with later versions of the Perl interpreter.

If you experience errors (especially if the program diagnostics report that all files are completely uploaded, but errors are still reported when attempting to run the individual subroutines), this is a problem with your Perl interpreter with which DiscusWare cannot help you.