条件语句

请注意，do...end 语法是常规关键字列表的语法糖，因此你实际上可以这样做：

unless false, do: IO.puts("Condition is false")
# Outputs "Condition is false"

# With an `else`:
if false, do: IO.puts("Condition is true"), else: IO.puts("Condition is false")
# Outputs "Condition is false"