It's very hacky and in no way the right way to go, but it works (however only for the exact case described above).
.myClass ul li:nth-child(2) {
content: '->';
position: absolute;
left: 10.5em;
background: #fff;
}
As mentioned by others, for a job like this, CSS is not right tool. Add some javascript to do this job, it's way better as it doesn't care about the user's text zoom for example (which would break the CSS "solution" probably).
var el = document.getElementsByClassName('myClass')[0].children[0].children[1];
var text = el.innerHTML;
el.innerHTML = text.replace('?','-->');
See DEMO for the vanilla js solution.
Though, even better would be to find the source of the question mark ?
, it looks like there's some encoding problem (utf-8?).