Handling varargs and closure in Groovy

gistfile1.groovy

def execute(... arguments) {
  if (arguments.head() instanceof Map) {
    def settings = arguments.head()
    if (arguments.last() instanceof Closure) {
      def callback = arguments.last()
      def commandArgs = arguments[1..(arguments.length - 2)]
      println([commandArgs, settings, callback])
    } else {
      def commandArgs = arguments[1..(arguments.length - 1)]
      println([commandArgs, settings])
    }
  } else {
    if (arguments.last() instanceof Closure) {
      def callback = arguments.last()
      def commandArgs = arguments[0..(arguments.length - 2)]
      println([commandArgs, callback])
    } else {
      def commandArgs = arguments[0..(arguments.length - 1)]
      println commandArgs
    }
  }
}

execute()

execute 'abc'
execute 'abc', pty: true
​execute('abc', pty: true) {}

execute 'abc', 'def'
execute 'abc', 'def', pty: true
execute('abc', 'def', pty: true) {}
​