sub foo {
        my $array = shift;
        my $copy  = [map {[@$_]} @$array];
        ... Changes in $copy won't affect $array ...
        return $copy;
    }

##</code><code>##

sub foo {
        my $array = shift;
        my @copy  = map {[@$_]} @$array;
        ... Changes in @copy won't affect @array ...
        return \@copy;
    }