combining graphs from GD::Graph in one image file

Does anybody know how I can get more than one graph on a single image
file generated by the GD:Graph module?

I need to generate a lot of histograms which cannot be combined into a
single chart but all of these charts should be combined into one big
image file (doesn't need to be pretty). I need to make a lot of these
so combining the images by hand would not be ideal - is there a way to
do this in GD:Graph?

Thanks a lot!

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