From the shader section of the manual:
Quote:

Passes can have arbitrary names, with the following exception (A7.60): If the first pass name contains the character sequence "_repeat", the pass is repeated for every skin of the model. After each pass the skins assigned to entSkin1..entSkin3 are incremented by 1. So if the model has 5 skins, the pass is repeated 5 times, with entSkin1 set to the model's first, second, third, fourth, and fifth skin in succession. This special method can be used to render an arbitrary number of skins, for instance for multitexture terrain with 4 or more textures.