Call of Duty puts players in the shoes of a foot soldier in the American, British, and Russian armies during the Second World War. These soldiers aren't the one-man armies of other games; these soldiers are just another cog in the war machine.
It is a GSC script preprocessor for modders, for every Call of Duty which are using GSCs. A full description can be found here: moddb.com/tutorials/pregsc
This tool lets you use some language elements, which are missing from GSC. For this, you have to work in a source folder, and the program will transform the code to proper GSC in another directory. It's also very good for compressing your scripts as much as possible.