Its been a while and I don't have the code at hand but I have done something similar using a Perl Tk canvas object. By using Northings & Eastings instead of Lat/Long I was able to plot as x-y points. I had data available in Northing Easting format and if I recall correctly it was all within the one zone.

Geography::CoCo man page (not on CPAN that I could see) will convert Lat/Lon to Northing/Easting (or grid) format.

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my $chainsaw = 'Perl';