sub purse
  {
    my $balance = shift;
    my $sub;
    $sub = sub { my ($who, $qty) = @_;
                 print "Paying $who $qty\n"
                   if ($balance - $qty) >= 0;
                 undef $sub
                   if $balance <= 0 };
  }

{
  my $payment = purse(10);
  for ([qw/mom 7/],
       [qw/dad 3/],
       [qw/myself 1/])
    {
      $payment->(@$_) if $payment;
    }
}