These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.53 s (backtrack: 0/20).

[ebuild  NS    ] dev-lang/lua-5.1.5-r200:5.1::gentoo [5.4.8:5.4::gentoo] USE="deprecated readline" 389 KiB
[ebuild  N     ] dev-lua/lua-bit32-5.3.5.1-r1::gentoo  USE="-test" LUA_TARGETS="lua5-1 -luajit" 53 KiB
[ebuild  N     ] dev-lua/luaposix-37.0::gentoo  USE="-doc" LUA_TARGETS="lua5-1 -lua5-3 -lua5-4 -luajit" 187 KiB
[ebuild  N     ] dev-lua/readline-3.3::gentoo  LUA_TARGETS="lua5-1 -lua5-3 -lua5-4 -luajit" 16 KiB

Total: 4 packages (3 new, 1 in new slot), Size of downloads: 643 KiB