[mod_python] Nested loops in PSP

I wonder what makes the comment in the outer loop significant. The first 
piece of code works, but the second doesn't. Is this a bug or have I 
misunderstood the syntax?

---
<%
for i in range(5):
    # begin
%>
<%= i %><br>
<%
    for j in range(5):
%>
<%= i %>, <%= j %><br>
<%
%>
---
<%
for i in range(5):
%>
<%= i %><br>
<%
    for j in range(5):
%>
<%= i %>, <%= j %><br>
<%
%>
---