def car = "Patriot"
	
def manufacturer = match(car) {
  when "Focus",     "Ford"
  when "Navigator", "Lincoln"
  when "Camry",     "Toyota"
  when "Civic",     "Honda"
  when "Patriot",   "Jeep"
  when "Jetta",     "VW"
  when "Ceyene",    "Porsche"
  when "Outback",   "Subaru"
  when "520i",      "BMW"
  when "Tundra",    "Nissan"
  otherwise         "Unknown"
}
	
println "The $car is made by $manufacturer"
	
def match(obj, closure) {
    closure.subject = obj
    closure.when = { value, result ->
        if (value == subject)
            throw new MatchResultException(result: result)
    }
    closure.otherwise = { return it }
    closure.resolveStrategy = Closure.DELEGATE_FIRST
    try {
        closure()
        closure.otherwise()
    } catch (MatchResultException r) {
        r.result
    }
}
	
class MatchResultException extends RuntimeException {
    def result
}

A nice example of utilizing Groovy closures in order to create a when statement in Groovy (http://www.transentia.com.au/flatpress/?x=entry:entry090311-222726).

Creating when construct in Groovy using closures

groovy

Groovy