You did pass a reference, but then you created a new array:

my @b = @$refA;
[download]

And then you modify that new array which is only scoped inside the function, which leaves the array-by-reference argument as-is.

If you change your function to look like this, it might do what you were expecting:

sub Foo
{
    my $refA = shift;
    $refA->[0] = "hello";
    $refA->[1] = "world";
    $refA->[2] = "Perl";
}
[download]

--
3dan