PDL is the Perl data language that offers number crunching capabilities for Perl. PDL ("Perl Data Language") gives standard Perl the ability to compactly store and speedily manipulate the large N-dimensional data arrays which are the bread and butter of scientific computing. PDL turns perl in to a free, array-oriented, numerical language similar to (but, we believe, better than) such commerical packages as IDL and MatLab. One can write simple perl expressions to manipulate entire numerical arrays all at once. For example, using PDL the perl variable $a can hold a 1024x1024 floating point image, it only takes 4MB of memory to store it and expressions like $a=sqrt($a)+2 manipulate the whole image in a few milliseconds. A simple interactive shell (perldl) is provided for use from the command line and a module (PDL) for use in perl scripts. The PDL distribution for Perl is free Software and provides extensive numerical and semi-numerical functionality with support for two- and three-dimensional visualisation as well as a variety of I/O formats. The goal is to allow PDL to interact with a variety of external numerical packages, graphics and visualisation systems. Easy interfacing to such systems is one of the core design features of PDL. Requirements: