Hey there, I

As I understand Perlin noise, it effectively generates a pseudo-random field at integral co-ordinates and blends them together in between. The pseudo-random numbers are based upon the map co-ordinates, so they automatically fit together. As described in the article it is a function in (x, y) rather than being chunk based, so you can generate as much or little as you like, and it will fit together as long as the co-ordinates fit together.