PSL: PLIB's Scripting Language.
In particular, in using PSL, you do not add any dependancies on your application. If the end user has the correct version of PLIB installed - then the scripting language is already there - for sure.
PSL is a very light-weight C-like language with some features borrowed from C++. It's also 'stackless' and very friendly to games applications.
There are two PSL documents:
Each application can extend PSL by providing additional built-in functions - so if you are a PSL programer then you'll probably need to read the documentation for whatever PSL-enabled application you are writing for. If you are writing a PSL-enabled application, then you'd better sit down and WRITE that document!