sub foo { return [0,1]; }
my $aref = foo();

##</code><code>##

sub foo { return (0,1); }
my $aref = [foo()];

##</code><code>##

sub foo {
    my @rv = (0,1);
    return wantarray() ? @rv : \@rv;
}
my $aref  = [foo()]; # wantarray() will be true, so the entire list gets passed back and then the square braces create and populate an array ref.
my $aref2 = foo();   # wantarray() will be false, so inside the subroutine we return a reference to the array.