Student Programming Language (SPL) a subset of PL/I
...In 1970 the compiler was modified by Robin A. Vowels at Royal Melbourne Institute of Technology to be more compatible with the PL/I language. The compiler is written in XPL using an MSP parser. XPL is described in the book "A Compiler Generator" by McKeeman, Horning and Wortman.
The XPS is a scalable platform for meta-programming and domain engineering. It provides a virtual machine, compiler, and runtime library that make it possible to efficiently develop, debug, and run programs based on XPL (eXtensible Programming Language)