The algorithm in lib.join is extremely slow, requiring allocation of a new string for every element in the array. Moreover, lib.join appears to do exactly the same as the standard function table.concat.

Suggestion: replace its definition by

lib.join = table.concat

In my experience (as a dependency of yaml) this works fine under Lua 5.4, but to get it one has to install via a side channel of some kind. Direct installation via luarocks install lub is blocked because of this version restriction:

I think this top end restriction should just be dropped and a new rockspec released and published on LuaRocks.org so that existing users can go on using it as usual without kludges.

I wanted to try dub, they seem to be lua scripts only, I see they require lub so here i am.
Excuse my ignorance but i cant see how to build lub.
Best
victor bombi