Games::Sequential is a framework for producing sequential games. Among 
other things it keeps track of the sequence of moves, and provides an 
unlimited undo() mechanism. It also has methods to clone() or take a 
snapshot() of a game.

Users must pass an object representing the initial state of the game as the 
first argument to new(). This object must provide the two methods copy() 
and apply(). You can use Games::Sequential::Position as a base class, in 
which case the copy() method will be provided for you. The apply() method 
must take a move and apply it to the current position, producing the next 
position in the game.