RiscLua is a small easily learnt programming language
for RISC OS. You can find a tutorial introduction to it
here in
RiscLua for Beginners and an example worked out in detail here in
RiscLua tips. You can also find a discussion of
similarities between BBC Basic and RiscLua.
For an introduction to the lpeg library, which provides
very powerful facilities for matching patterns and catching data
within text, see
Around PEGs or
Parser expression Grammars.
The RiscLua package consists of an application !lua,
that contains its own documentation.