Placemat is an evolving file format. In the current build it is able to handle a small subset of commands. Placemat takes in .plmat files and outputs .html
Placemat runs from the terminal after installation, by simply pointing to a .plmat file. It will render an html version of that file in the working directory. the -c argument passes the file name to render.
So given the directory structure
dir/ / myfile.plmat
you could run placemat to compile your file with the following terminal commands.
cd dir placemat -c myfile.plmat
This would yield
dir/ / myfile.plmat / myfile.html