downvoted because it's confusing. OP is about groovy and if people scan-read quickly the answers, we might think it's a valid groovy syntax proposed. See similar questions with these tags.
What is the "?:" operator used for in Groovy? - Stack Overflow
In Groovy you also have to be aware that in addition to ==, alias "Match operator", there is also =, alias "Find Operator" and ~, alias "Pattern operator". All are explained here.
In groovy, the bitwise operators can be overridden with the leftShift (<<) and rightShift (>>) methods defined on the class. It's idiomatic groovy to use the leftShift method for append actions on strings, buffers, streams, arrays, etc and thats what you're seeing here.
In examples of groovy code I find the -> operator everywhere, but the groovy tutorials nor the book I have seem to provide any explaination as to what this means.
In a Groovy script the scoping can be different than expected. That is because a Groovy script in itself is a class with a method that will run the code, but that is all done runtime. We can define a variable to be scoped to the script by either omitting the type definition or in Groovy 1.8 we can add the @Field annotation.
What is Grails? Grails (previously known as "Groovy on Grails") is a programming framework based on Groovy and inspired by Ruby on Rails (there are differences, but there are lots of similarities too). Like RoR, Grails promotes "coding by convention", development best practices, and is meant to be highly productive.
What are "Groovy" and "Grails" and what kinds of applications are built ...