It depends upon what you're trying to achieve.

1. If you just want the variables to be accessible by the handler using them, then using closures are the simplest option:

   {
       my $n = 0;
       sub handler {
           my $tid = threads->self->tid;
           for( 1 .. 5e5 ) {
               usleep( 100 );
               print "$tid: ", $n++;
           }
       }
   }
   [download]

   Each handler will get it's own copy of $n above and can use it without concerns for locking or sharing. It retains it's value across calls to the handler.

2. If you need to share the data either between the handlers, or between each handler and the main thread, then that requires the data be shared. And that comes with the inherent need for locking.

   Isolating your users from the requirements of shared data is possible, but distinctly non-trivial.

   I am reluctant to expend energy describing possible approached until I:

   1. know that's what you want.
   2. impose upon you for a more complete description of the types of data and uses to which you envisage it will be put.