Hi all, I'm pretty new to Perl. I'm trying to write a function which takes as input a 2D matrix of 0s and 1s(adjacency matrix) and changes a 0 value to 1 once where it finds a 0. The function is supposed to return the new matrix, without changing the old matrix which is passed as an argument to this function. 
sub add_edge {
    my (@graph) = @_;
    my $node1 = int(rand(5));
    my $node2 = int(rand(5));
    print "Random node = $node1\n";
    print "Random node = $node2\n";
    my $i, $j;
    if (($node1 ne $node2) and ($graph[$node1][$node2] eq 0)) {
        $graph[$node1][$node2] = 1;
        return $graph;
    }
    for ($i = 0; $i < $graph_size; $i++) {
    for ($j = 0; $i < $graph_size; $j++) {
        if (($graph[$i][$j] eq 0) and ($i ne $j)) {
        $graph[$i][$j] = 1;
        return @graph;
        }
    }
    }
}

[download]

Suppose my @G is a 5x5 matrix of all 0s. 
@H = add_edge(@G);

[download]
If I write the above statement, I get the desired result in @H. But, it also modifies my original array @G, which I don't want to happen. So, what I'm seeking here is how to pass an array to a function and return as result another array which doesn't modify the original array.

Any suggestions would be highly appreciated.
Thanks.

In reply to How to return a two dimensional array from a function in Perl? by gunners.newark

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