That's odd. It should overload numerification and numerical ops instead of (or in additon to) stringification.

There is only one case where stringification is needed that comes to mind: When the function behaves differently whether a parameter is a string* or an object, and the parameter is an object with an overloaded stringification operator. For example,

sub output {
   my ($fh, ...) = @_

   if (!ref($fh) && ref($fh) ne 'GLOB') {
      open($fh, '>>', $fh);
   }

   ...
}
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* or number vs object, or boolean vs object