use strict;             # leak occurs whether strict is used or not
 
my $fact = build_sub();
while(1) {
  print &$fact(5), $/;
}
 
sub build_sub {
  my $factorial_sub_ref;
 
  $factorial_sub_ref = sub {
    my ($number) = @_;
    if ($number < 2) { return 1; }
    return($number * &$factorial_sub_ref($number - 1));
  };
 
   return $factorial_sub_ref;
}