// Declare the function
function daysInMonth(int month)
{
  switch
  {
    when (contains(set s = (4, 6, 9, 11), month)) 30;
    when (month == 2) 28;
    when (contains(set s = (1, 3, 5, 7, 8, 10, 12), month)) 30;
    otherwise throw("Bad month number " + month);
  }
}

int month = 13;
writeln($catalog.system.out, "There are " +
                             call daysInMonth(month = 1) +
                             " days in January");

writeln($catalog.system.out, "February (most often) has " +
                             call daysInMonth(month = 2));

writeln($catalog.system.out, "Lets croak " +
                             call daysInMonth(month = 13));