This definitely strikes me as a bug. Per Programming Perl...

If you have a local that looks like this:

     {
         local $var = $newvalue;
         some_func();
         ...
     }
[download]

you can think of it purely in terms of run-time assignments:

     {
         $oldvalue = $var;
         $var = $newvalue;
         some_func();
         ...
     }
     continue {
         $var = $oldvalue;
     }
[download]

The difference is that with local the value is restored no matter how you exit the block, even if you prematurely return from that scope.

Regardless of or what variable you are local'ing in your sub, it should return it to it's orriginal value on exit -- and it certainly shouldn't affect the callers scope.