I've only recently started using Mason myself, so this may have nothing to do with your problem, but this syntax:

<%perl>
<!- perl>
[download]

is brand new to me. I thought the correct syntax was:

<%perl>
</%perl>
[download]

Similarly for your other <%init>, <%args>, etc. sections.

As I said, I'm brand new to Mason, so this may be an alternative syntax I'm not aware of. Is it? (You may want to try the more "canonical" syntax and see if the error moves.)

HTH