my $EPSILON = 1e-20;
my $asum = GreenTheoremTest($poly);
if (abs($asum) < $EPSILON) {
   print "Polygon area is too small to be sure of direction!\n";
} elsif ($asum < 0.0) {
   print "Polygon is clockwise\n";
} else {
   print "Polygon is counterclockwise\n";
}