#12 Data::Dumper by URL param

[Gryphon Shafer]

If, when in DEVEL mode only, a user appends "data=1" or
"data=on" or whatever to the end of a URL, the template
won't render HTML but rather call Data::Dumper and spit
back all the parameters sent to the template.

This will likely mean subclassing HTML::Template and
overriding param() and output().