Saving a picture contained in a web page to disk

[Giulio Cespuglio]

Hi there,

I would like to save to disk a picture contained in a webpage. 

Unfortunately the image is dynamic, so the url is actually a query
which looks like

http://adfarm.mediaplex.com/ad/bn/2397-11787-1843-5?mpt=1068644406357385

rather than the standard

http://img-cdn.mediaplex.com/ads/2397/11787/q2_dell_inspiron_120x600.gif

I've been told that a scripting language like Perl, Python or PHP is
my best bet for this kind of tasks, would you agree? 
Could you please give a few function names to look at as a starting
point?
That should suffice, although a code snippet would be greatly
appreciated.
;)

Thank you very much in advance for your help.

Regards,
Giulio