PDL stands for the Perl Data Language, and is a set of Perl Extensions and
Modules to compactly store and speedily manipulate large N-dimensional
tensors. Such manipulations are useful for scientific and engineering
calculations that involve a lot of manipulations of vectors, matrices and
other tensors.

With PDL one can create and fill in large tensors, and perform element by
element operations on them (product, addition, subtraction, division, taking
the sine, cosine, logarithm etc), as well as multiply matrices, etc. The
routines for doing this are hard-coded in C, and so are performed very quickly.

PDL aims to be a viable alternative to packages such as Matlab or Scilab
while giving all the power of Perl. At the moment it still lacks a lot
of functionality.

I already used PDL once for a script I wrote to determine a close-to-optimal
way to switch between game AI scans to solve a range of boards. With PDL
I was able to run it quickly and still enjoy having to write and debug Perl
code.