package Base;

sub new {
    my $class = shift;
    my $self = { FSM => {First => { fail_a => 'Second',
                                    fail_b => 'Third',
                                    pass   => undef },  # we're done
                         Second =>{ fail_c => 'Third',
                                    pass   => undef )} };
    bless $self, $class;
    return $self;
}

package First;
use base qw( Base );

sub new {
  # ...
}

package Second;
use base qw( Base );

sub new {
  # ...
}

# ... and so on