Did a quick search and found that the '@' operator is matrix multiplication.

So that line points @ matrix.T is multiplying the matrix 'points' by the transpose of 'matrix'.

I'd say this really should be translated to PDL, because otherwise it's going to get very verbose. That's the real reason people use matrices in linear algebra - it is just too much fiddly math otherwise, and it's all fairly repetitive. Mathmaticians created "matrix math" just to simplify the notation for these common formulas. Unfortunately I don't know PDL so I can't help there.