JSFiddle - React, Tailwind, and code Playground

HTML

<span class="halfright">Hello world!</span>

CSS

.halfright {
    border-top:1px solid black;
    position: relative;
    padding-right:3px;
}
.halfright:after {
    content: "";
    display:block;
    width:50%;
    height:1px;
    padding:0;margin:0;
    background-color:white;
    position: absolute;
    right:0;
    top:-1px;
}