How to use global functions?

In one script I have this code:

_G["chick"] = function() print("chicken") end

And in another script I have this code that activates on tool click:

_G.chick()

But I get this message: attempt to call field 'chick' (a nil value)

Even with the command line I get the same message.

How should I do this? I can tell my code will be terrible if I have to copypaste through every tool.