To paraphrase what demerphq said :

• Your "two_hard" sub returns an array (@_).
• Your "print" statement uses the concat "." operator, which makes the usage of the return value in a scalar context
• In a scalar context, an array evaluates to the number of elements (2)

Similarly, your "two_easy" sub returns a LIST. (Because you picked out elements of the array, using an array slice).

In a scalar context, a list evaluates to the last element.

For now, you can ignore the "tied" comment.

Update: jdporter is apparently a faster typist than I am. His post essentially says the same thing.