artist's answer is correct. To expand upon it, if you want to do this in a portable fashion, or the directory with your script and GD.pm might change, use the standard FindBin module:

use FindBin;
use lib $FindBin::Bin;
[download]

The above code will add the directory where your script resides (well, technically the current working directory of your script when FindBin was used) to the library searchpath.

CU
Robartes-