在声明性Jenkins脚本块中，如何在执行命令时引用变量？

pipeline {
    agent any
    stages {
        stage('Example') {
            steps {
                script {
                    def myVariable = 'Hello World'
                    sh "echo ${myVariable}"
                }
            }
        }
    }
}

pipeline {
    agent any
    stages {
        stage('Example') {
            steps {
                script {
                    def myVariable = 'Hello World'
                    sh 'echo ${myVariable}'
                }
            }
        }
    }
}

pipeline {
    agent any
    environment {
        MY_VARIABLE = 'Hello World'
    }
    stages {
        stage('Example') {
            steps {
                script {
                    sh "echo ${env.MY_VARIABLE}"
                }
            }
        }
    }
}