JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>Первый
    </li><li>Второй
    </li><li>Третий</li>
</ul>

CSS

ul {
    margin: 0;
    padding: 4px;
    background: linear-gradient(#999, #555);
}
li {
    display: inline-block;
    padding: 5px 10px;
}

li:not(:last-child) {
    border-right: 1px solid #aaa;
    
}

li:not(:first-child) {
    border-left: 1px solid #444;
    
}