While I was working hard on excygen's own functional programming language in the past weeks (or even months?), it turned out to be a big project in its own to create a real, mature, robust programming language.
I ditched any further effort for now, for sake of an earlier 0.1 release, and for sake of a bigger user base being able to create new height functions, using ... (drum roll) ... Python. Whohoo!
Libnoise, a library for Perlin Noise and more, will be available in your Python scripts.
To summarize: You can use Python, with Perlin noise for free, to create your terrain formations (once 0.1 is released), and it will be as easy as ...
return u * v
or as complex as ...
perlin = Libnoise.Perlin()
foo = 0
for x in range(0,100)
foo = foo * perlin(u,v) + sqrt(perlin(u,v+sin(x)))