$roger = new Employee::Casual( rate => 14.00 );
   $sally = new Employee::FullTime( salary => 50_000 );
   $mark  = new Employee::FullTime( wage => 12.00 );

   $roger->add_hours( 8 ); # worked 8 hours
   $sally->add_hours( 8 ); # worked 8 hours
   $mark->add_hours( 8 ); # worked 8 hours

   # Now pay them
   $roger->write_check(); # 14 * 8  =  $112.00
   $sally->write_check(); # $0.00 - nothing due to a full timer until fortnight is accounted for
   $mark->write_check(); # $0.00 - same here

   # add another 11 days
   # ... same as above, 11 times ...

   # then on day 13, it's a long day
   $roger->add_hours( 10 ); # worked 10 hours
   $sally->add_hours( 10 ); # worked 10 hours
   $mark->add_hours( 10 ); # worked 10 hours

   # So then they take day 14 off
   $roger->sick_leave( 8 ); # 8 hours
   $sally->sick_leave( 8 );  # 8 hours
   $mark->sick_leave( 8 ); # 8 hours

   # and get a work log:
   $roger->write_check(); 
      # 11 days * 8 hours + 1 day * 10 hours = 98 hours @ $14.00 = $1372 
      # (no sick pay for casuals and we've already paid him for day 1)
   $sally->write_check(); 
      # 14 days @ ($50000 / 365 days)  = $1917
      # (no overtime for sallary earners)
   $mark->write_check(); 
      # 12 days * 8 hours + 1 day * 10 hours = 106 hours @ $12.00 = $1272

   # get entitlements
   $roger->leave_entitlements(); # {sick_leave => 0, annual_leave => 0} - none for the casual
   $sally->leave_entitlements(); #  {sick_leave => 56, annual_leave => 8.6}
   $mark->leave_entitlements(); #  {sick_leave => 56, annual_leave => 8.6}