<%def name="summer(lst)">
  <%
     result = 0
     for elem in lst:
         result = result + elem
  %>
  The sum of ${lst} is ${result}.
</%def>

<%def name="product(lst)" filter="trim">
  <%
     result = 1
     for elem in lst:
         result = result * elem
  %>
  The product of ${lst} is ${result}
</%def>

Summer  : ${summer([10, 20, 30, 40, 50])}
Product : ${product([10, 20, 30, 40, 50])}