I really don't know how to name this question, it's great if anyone with 2K+ rep can edit this title to better reflect my question (the fact that I can't name this easily is probably why I can't Google the solution).

I've got this, which is working:

<c:choose>
    <c:when test="${sometest}">
        Hello, world!
    </c:when>
    <c:otherwise>
        <fmt:message key="${page.title}" />
    </c:otherwise>
</c:choose>

And I want to change it to this:

<c:choose>
    <c:when test="${sometest}">
        <c:set var="somevar" scope="page" value="Hello, world!"/>
    </c:when>
    <c:otherwise>
        <c:set var="somevar" scope="page" value="<fmt:message key="${page.title}">"
    </c:otherwise>
</c:choose

But of course the following line ain't correct:

<c:set var="somevar" scope="page" value="<fmt:message key="${page.title}">"

How can I assign to the somevar variable the string resulting from a call?