# This variant of perl bank accounts use a hash table in place of the
# dispatch procedure.  

sub makeaccount
{  my $balance = $_[0];

   my $deposit = sub { $balance += $_[0]; $balance; };

   my $withdraw = sub { if ($_[0]<=$balance) 
			     { $balance-=$_[0]; $balance; } 
                        else { print "insufficient funds\n"; }
                      };

   my $inquiry = sub { $balance };

   my $dispatch;  # use hash table as an interface

   $dispatch->{withdraw} = $withdraw;
   $dispatch->{"deposit"} = $deposit;   # strings are ok too
   $dispatch->{inquiry} = $inquiry;

   $dispatch;  # makeaccount returns dispatching hash table
}

my $ac1 = makeaccount 100;
my $ac2 = makeaccount 500;
$ac1->{withdraw}->(50);  
print $ac1->{inquiry}->();

# One important difference between the hash table approach and the
# interface (dispatch) function approach is that everything you enter
# into the hash table is "public".