Perl module to calculate a convex hull using Andrew's monotone chain algorithm

 Math::ConvexHull::MonotoneChain optionally exports a single function
 convex_hull which calculates the convex hull of the input points and returns
 it. Andrew's monotone chain convex hull algorithm constructs the convex hull
 of a set of 2-dimensional points in O(n*log(n)) time.
 .
 It does so by first sorting the points lexicographically (first by
 x-coordinate, and in case of a tie, by y-coordinate), and then constructing
 upper and lower hulls of the points in O(n) time. It should be somewhat faster
 than a plain Graham's scan (also O(n*log(n))) in practice since it avoids polar
 coordinates.