Don't use opaque globals.

mods/mcljepc_core/blocks.lua

@@ -6,12 +6,13 @@ local blocks = {
 		-- Color picked to be much lighter than above from MCL2, but still mostly green
 		color = "#58ff3a",
 		tiles = { "mcl_core_grass_block_top.png" }
-		-- tiles = { terrain(0) }
+		-- TODO make this a setting
+		-- tiles = { mcljepc_core.helpers.terrain(0) }
 	},
 	cobblestone = {
 		description = "Cobblestone",
 		tiles = { "default_cobble.png" },
-		-- tiles = { terrain(1) }
+		-- tiles = { mcljepc_core.helpers.terrain(1) }
 	}
 }
 

mods/mcljepc_core/helpers.lua

@@ -1,12 +1,13 @@
 --- Misc. Helper functions
+mcljepc_core.helpers = {}
 
-function atlas_id(tex, id)
+function mcljepc_core.helpers.atlas_id(tex, id)
 	local x = id % 16
 	local y = math.floor(id / 16)
 
 	return tex..".png^[sheet:16x16:"..x..","..y
 end
 
-function terrain(id)
+function mcljepc_core.helpers.terrain(id)
 	return atlas_id("terrain", id)
 end

mods/mcljepc_core/init.lua

@@ -1,3 +1,4 @@
+mcljepc_core = {}
 dofile(minetest.get_modpath("mcljepc_core") .. "/helpers.lua")
 dofile(minetest.get_modpath("mcljepc_core") .. "/blocks.lua")