I am using the good old fisher-yates shuffle from perlfaq4:

  my $ref = \@list;

  for (my $i = @$ref; --$i; ) {
    my $j = int rand ($i+1);
    next if $i == $j;
    @$ref[$i,$j] = @$ref[$j,$i];
  }

  # @list is modified in place

[download]

Question: why do I have to use a reference? I can't figure this out. I tried:

  for (my $i = scalar(@list); --$i; ) {
    my $j = int rand ($i+1);
    next if $i == $j;
    @list[$i,$j] = @list[$j,$i];
  }

[download]

This didn't work... Some elements were duplicated in the changed list. This is probably just a lack of understanding references well, but could some monk please explain this?

</ajdelore>

In reply to Why do I need to shuffle an array by reference? by ajdelore

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