To answer this question, let's break down the given code:
my @a = ([1, 2, 3, 4], [5, 6, 7, 8]);
print join(' ', @{$a[1]}[1..3]);
In the first line, an array @a is declared and initialized with two array references: [1, 2, 3, 4] and [5, 6, 7, 8].
In the second line, the print statement is used to output the result. The join function is used to concatenate the elements of an array with a specified delimiter. In this case, the delimiter is a space ' '.
The expression @{$a[1]}[1..3] is used to access the elements from the second array reference ($a[1]) using array dereferencing (@{}) and array slicing ([1..3]). This means we are accessing elements 1, 2, and 3 from the second array.
Therefore, the output of the print statement will be 6 7 8, which corresponds to option D: "6 7 8".