title: Using "$" in Groovy
body: <p>I see { } are used for closures, and then I believe when a $ is put in front of braces, it is simply doing a variable substitution within a string.  I can't find the documentation on how the $ works in the reference ... hard to search on it unfortunately, and the Groovy String documentation is lacking in introducing this.  Can you please point me to the documentation and/or explain the "$" operator in Groovy -- how all it can be used?   Does Grails extend it at all beyond Groovy?</p>