draw-polygon.scm

This sounds a very interesting script indeed ! Unfortunately for me, I have had this message :

"Error while executing script-fu-draw-polygon:

Error: ( : 1) Bad syntax of binding spec in let* : ((segment) (segment (make-vector 4)) (stepx dx) (stepy dy) (raggio Radius) (nlati Lati) (angolo) (arco) (beta) (gamma) (gcount) (npoint)) "

{I used the 2.4 version under Gimp 2.8}
Does anyone know what to do or what I did wrong ?
Thanks
Pierre