sub func {
    my(...) = @_;
    my @new_a;
    # assume some assignment to @new_a based on params
    for(....) {}
    wantarray? @new_a: \@new_a;
}
# this one gets you a reference to @new_a in &func()
# which is available as long as $ar_array is in scope
my $ar_array = &func(...);
# this is the copy of @new_a from &func()
# @new_a is gone
my @array = &func(...);

Also:
wantarray? @foo: "@foo"
wantarray? @foo: $foo[0]
aren't nearly the same except the first above is an
implicit join to scalar and the second is the first element
which may or may not be what you want.