I'm not familiar with GIFGraph either, but would recommend you consider using gnuplot. All you'd need to do is output all the (x,y) values to a file (coordinates whitespace separated, one point per line) from your Perl script, and gnuplot will make a nice graph from it.. just tell gnuplot plot 'datafile' with lines. Alternatively, there seem to be a few gnuplot interfaces for Perl on CPAN. In terms of plotting software, I believe gnuplot is very robust, and I've found there's usually a way to plot whatever I want with it.

Sorry I can't give on-point advice about GIFGraph, but I hope this helps.

blokhead