$ luarocks install lsleep
lsleep contains cross-platform implementations of sleep (Sleep in Windows) and usleep (CreateWaitableTimer.... whatever).
If you're requiring LuaSocket and don't need subsecond sleeping, then you don't need this. LuaSocket has sleep included. I just thought it was weird that there was no way to sleep without requiring a socket library.
Versions
Dependencies
lua >= 5.2