<p class="beginning">
 beginning
</p>
<p class="middle">
 middle
</p>
<p class="end">
 end
</p>

/* New Level 4 version */
p:is(.beginning, .middle) {
    color: blue;
}

/* Old Level 4 version, only supported by Safari */
p:matches(.beginning, .middle) {
    color: blue;
}

/* Old Level 4 version, for Webkit browsers */
p:-webkit-any(.beginning, .middle) {
    color: blue;
}

/* Old Level 4 version, for Firefox browsers */
p:-moz-any(.beginning, .middle) {
    color: blue;
}