switch picks an alternative

Although if is handy when there are two alternatives, it can be more convenient to use switch when there are many choices.

switch is used together with when and (optionally) else. Here is how switch works:

d = "w"
switch d
  when "m"
    write "Monday"
  when "t"
    write "Tuesday"
  when "w"
    write "Wednesday"
  when "th", "thu"
    write "Thursday"
  when "f"
    write "Friday"
  else
    write "Someday"

The first alternative that matches the switched value is the one that runs.

The indentation pattern in a switch is important: each when must be indented, and they all should line up with each other.