[Plplot-general] can't run plplot with sbcl (wheezy debian)

[gerard <g.r...@fr...>]

Hello,
in the file system-examples.lisp I have : (defparameter gdev "svg")  

*
(load "system-examples.lisp") 
T

* (system-examples::plot )
Enter graphics output file name: dessin2.svg

*
nothing happens : no error, no graphic

How can I make flplot run  correctly ?

Thanks in advance for help or a link to an understandable tutorial.

Gerard