 <p>Use <code>|</code> and not <code>OR</code> for multiple choices, thus making code like:</p> <pre><code>with ALUop select z &lt;= s_add_sub when "00000" | "00001" | "00010" | "00011", x AND y when "00100", ... </code></pre> <p>This is similar to the syntax for multiple choices to <code>case</code>.</p>