sub leak_mem {
  my $foo;  # foo data has one reference, the 'foo' name
  my $bar;  # bar data has one reference, the 'bar' name
  $foo = \$bar;  # bar data has two refs
  $bar = \$foo;  # foo data has two refs
  return 1;
  # Oops. foo and bar data reference count are both
  # decremented by one (because the foo and bar names have
  # just gone out of scope), but that doesn't take them
  # to zero.
  # We just lost some bytes, sir.
}