While investigating

`Benchmark.pm` I decided to try benchmarking different sorting algorithms, and have run into trouble with my implementation of <dfn>Merge Sort</dfn>;

`sub Merge(@) {
my @array = @_;
MergeSort (0, $#array);
return @array;
sub MergeSort($$) {
my $first = shift;
my $last = shift;
if ($last>$first) {
my $mid = int(($last+$first)/2);
MergeSort($first, $mid);
MergeSort($mid+1, $last);
my @b;
@b = ( @array[$first..$mid], @array[reverse($mid+1..$last)] );
my ($i, $j, $k) = (0, $last-$first, $first);
for (; $k<=$last; $k++) {
$array[$k] = ($b[$i]<$b[$j]) ? $b[$i++] : $b[$j--];
}
}
}
}
`

The function works perfectly, but with warnings turned on, spits out the following:

`Variable "@array" will not stay shared at ./benchmark-sort.pl line [x]
+.
`

Where

`[x]` is the first line in

`MergeSort()` which manipulates

`@array`.

Presumably I'm doing something naive here to do with the scoping of

`@array`, which, in slightly different circumstances, could cause errors rather than just warnings.

So, what does the warning mean, and how should I declare

`@array` to avoid it?