Actually I can see useful applications for this.
in reply to Perl allows you to change the definition of false to make it true. (And vice versa.)
When trying to convert (and not just interpret) other languages like LISP or JS to Perl one of the biggest problems are implicit typeconversions at edgecases.
(Thoroughly catching all those edgecases slows such conversions ridiculously down!)
For instance this way, one could try to patch booleans in a way that they stringify to "false" and "true" like in JS.
Thanks for showing! =)