with_items个人理解就像是shell里面的循环，可以循环操作
简单案例一：
多个变量
- name: installpakger
yum: name={{ item }} state=latest ##安装依赖包
with_items:
- openssl-devel
- pcre-devel
- gcc
简单案例二：
k/v类型
- hosts: CentOS-7-4
gather_facts: false
tasks:
- name: copy files
copy:
src: "{{ item.src }}"
dest: "{{ item.dest }}"
with_items:
- { src: "/home/ansible/copy.yml", dest: "/home/copy.yml" }