How to make "struct" Lua scripts?

Here an example:
When you change and save the Lua structure script of the tool (lua\entities\weapons\gmod_tool\stools\anytool.lua), all tools are updated and loaded in game, including the base ones. In this case, you do not declare the global variable TOOL in the file.

How do I load my Lua scripts with include(“myscript.lua”) like that so that they are loaded with custom global variables into the game when changing?