Lua version 5.4 was released at the
end of June; it is the fifteenth major version of the lightweight scripting
language since its creation in 1993. New in 5.4 is
a generational
mode for the garbage collector, which performs better for programs with
lots of short-lived allocations. The language now supports “attributes” on
local variables, allowing developers to mark variables as constant
(const) or resources as closeable (close). There were
also significant performance improvements over 5.3 along with a host of
minor changes.

Source: LWN.net – [$] What’s new in Lua 5.4