SPUG:Resetting a closure's memory

[Sanford Morton]

Closures are typically used to create a private memory for a
subroutine.  What's the best way to clear this memory and reset the
closure--as if the closure were being called for the first time?

All I can think of is to pass a variable to the closure asking it to
reset itself, but I was wondering if there were a more elegant way.

( my $private = undef;
  sub aSub {
      my $amnesia = shift;
      $private = undef if $amnesia;
      ....
  }
}