Template::Toolkit subclass with automatic filtering

 Template::AutoFilter is a subclass of Template::Toolkit which loads a
 specific Parser that is subclassed from Template::Parser. It adds a filter
 instruction to each interpolation token found in templates loaded by the TT
 engine. Tokens that already have a filter instruction are left unchanged.
 .
 By default this automatic filter is set to be 'html', but can be modified
 during object creation by passing the AUTO_FILTER option with the name of the
 wanted filter.
 .
 Additionally a pass-through filter called 'none' is added to the object to
 allow exclusion of tokens from being filtered.
 .
 Lastly, if you have problems with the directives which get auto filters
 applied, you can see the Template::AutoFilter::Parser docs for how you can
 customize that.