Including a groovy script in another groovy

I have read how to simply import a groovy file in another groovy script

I want to define common functions in one groovy file and call those functions from other groovy files.

I understand this would be using Groovy like a scripting language i.e, I dont need classes/objects. I am trying to something like dsl that can be done in groovy. All variables will be asserted from Java and I want to execute groovy script in a shell.

Is this possible at all ? Can someone provide some example.