如何用原生的vimscript产生需要的css文本?

Question

有个有规律的css文件需要产生

.item1{
    background-image:url("img/item1_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item1:hover{
    background-image:url("img/item1_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

.item2{
    background-image:url("img/item2_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item2:hover{
    background-image:url("img/item2_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

.item3{
    background-image:url("img/item3_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item3:hover{
    background-image:url("img/item3_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

.item4{
    background-image:url("img/item4_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item4:hover{
    background-image:url("img/item4_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

.item5{
    background-image:url("img/item5_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item5:hover{
    background-image:url("img/item5_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

为了产生上面的css文件，我使用了下面的bash
（有个实际的网页，我通过这种方式产生了12个,测试通过)

for i in `seq 1 5`;
do
echo "
.item$i{
    background-image:url(\"img/item${i}_1.jpg\");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item$i:hover{
    background-image:url(\"img/item${i}_2.jpg\");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}"
done

现在想偷懒到底。
假定，vim已经有文档

.item1{
    background-image:url("img/item1_1.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}
 
.item1:hover{
    background-image:url("img/item1_2.jpg");
    background-repeat: no-repeat;
    background-position: 0px 0px;
}

或为了产生最终结果，有类似的文本先摆上。

如何进入vim的命令行状态，输入几个命令后，正在编辑的文件就变成了我需要的css文件（别再提vim调用bash的方法了，用vimscript)？