My thoughts, some of which may be redundant:

1. Set stack size at threads object construction:

   my $thr = threads->new(stack_size => 65535);
   [download]

2. Or set the default during import:

   use threads { default_stack => 65535 };
   [download]

3. Or set stack size for a given thread:

   $thr->create({stack=>65535}, 'function', 'arg1','arg2');
   [download]

   If the first option is a HashRef, treat it as options to create(); if it's a scalar, it's the function name (old-style call).
4. Or, instead of the above, use a separate method:

   $thr->create('function','arg1','arg2'); # use defaults
   $thr->create_with(
      -call   => 'function',
      -args   => ['arg1','arg2'],
      -stack  => 65535
   );
   [download]

5. And still allow runtime changes to (and discovery of) settigs:

   my $stack = $thr->get_stack_size() + 1024;
   $thr->set_stack_size($stack) if $stack <= 2048;
   [download]

I know I mixed naming conventions for the stack size parameters; I did this to suggest several alternatives, and not to suggest that the chosen convention should be anything but consistent.