Well, I cheated and ran the script to see what would happen.
But I will offer a guessed explanation.

The first script I ran was as is shown above. My output was:

"In the beginning there was , in the end there will be .
"
[download]

B: I believe the output was this way because when the subroutine
was called via the subroutine(); nothing was passed to the subroutine via the '()' thus there
were no valid local (to the subroutine) variables called
'_' therefore nothing being substituted in those slots.

C: On the other hand when you change the subroutine(); to &subroutine; it printed:

"In the beginning there was nothing, in the end there will be nothing.
"
[download]

The reason this occurred is because when calling a subroutine
with the '&' the sub automagically "sees" the global scalar
array named '_'.

I admit, lexical scope vs dynamic scope is still confusing to me and
arrays with scope are questionable by me too. I'd be
interested to know how close I am to being correct.