gistfile1.txt

def dsl = '''
person.is { 
    name 'taro'
    age '28'
}.say()
'''

def impl = '''
def getPerson(){
    new Person()
}

class Person{
    def Person(){
        def mc = new ExpandoMetaClass( Person, false, true)
        mc.initialize()
        this.metaClass = mc
    }

    def is(Closure closure){
        closure.delegate = this
        closure()
        return this
    }
    
    def methodMissing(String name, args){
        this.metaClass."${name}" = args[0]
    }
    
    def say(){
        println "I am ${this.name}. ${this.age} old."
    }
}
'''

def script = """
${dsl}
${impl}
"""

new GroovyShell().evaluate(script)

I am taro. 28 old.