#!/usr/bin/perl

use GD::Simple;

my $i = GD::Simple->new(640,480);

$i->bgcolor('white');
$i->fgcolor('black');

my @a = (
... first values ...
);
my @b = (
... second values ...
);

for (\@a,\@b) {
    while (@$_) {
        my @x = splice @$_,0,2;
        next unless @$_;
        $i->moveTo(@x);
        $i->lineTo(@{$_}[0,1]);
    }
}
open $x, ">","out.jpg";
binmode $x;
print $x $i->jpeg();
close $x;