r><td><span class="term"><i><tt>ctxt</tt></i>:</span></td><td>the expression context</td></tr><tr><td><span class="term"><i><tt>exp</tt></i>:</span></td><td>the expression</td></tr><tr><td><span class="term"><i><tt>tokList</tt></i>:</span></td><td>where to store the tokens</td></tr><tr><td><span class="term"><i><tt>len</tt></i>:</span></td><td>the allocated length of @list</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the number of unique strings found, -1 in case of errors and