Groovy: wrap variable number of nested Closure calls #groovy

wrapperDemo.groovy

/**
 *  Class Wrapper allows to wrap and execute variable number of nested Closures.
 *  Immediately-wrapped closure is accessible inside the wrapper as variable `_`.
 */
final class Wrapper {
    private final List stack = []

    Wrapper leftShift(Closure c) {
        c.resolveStrategy = Closure.DELEGATE_FIRST
        stack << c
        return this
    }

    void unroll() {
        _unroll stack
    }
    
    private void _unroll(List x) {
        if (!x) {
            return
        }
        def current = x.last()
        current.delegate = [
            _:  x.size() == 1 
                ?   {} 
                :   { _unroll x.init() }
        ]
        current.call()
    }
}


(new Wrapper() <<
    {   println 'abc' } <<
    {   for (i in 1..3) { 
            _.call()
        }
    } << 
    {   for (i in 1..2) { 
            print 'ghi '
            _.call()
        }
    }
).unroll()​