sub add_expense { # takes Expense object as argument and adds it to _EXPENSES array
    my $self = shift;
    my $newexp = shift;
    my @expenses = @{$self->{_EXPENSES}};
    $newexp->{_ID} = $#expenses + 1;
    push(@expenses,$newexp);
    $self->{_EXPENSES} = \@expenses;
}

##</code><code>##

    my $self = shift;
    my $newexp = shift;

##</code><code>##

my ($self, $newexp) = @_;

##</code><code>##

my @expenses = @{$self->{_EXPENSES}};

##</code><code>##

sub add_expense { # takes Expense object as argument and adds it to _EXPENSES array
    my ($self, $newexp) = shift;
    $self->{_EXPENSES}{$newexp} = $newexp;
}