IO::Tee objects can be used to multiplex input and output in two different
ways. The first way is to multiplex output to zero or more output handles.
The IO::Tee constructor, given a list of output handles, returns a tied
handle that can be written to. When written to (using print or printf), the
IO::Tee object multiplexes the output to the list of handles originally
passed to the constructor. As a shortcut, you can also directly pass a
string or an array reference to the constructor, in which case
IO::File::new is called for you with the specified argument or arguments.