Yes, but is it a useful copy? The question was about an extra reference-dereference pair that makes a copy of a copy. What do you get for that work?

Just about nothing. There is no reason that I can see to prefer: 

sub foo {
  my @foo = @{[@{$_[0]}]};
  # etc
}

[download]
over 
sub foo {
  my @foo = @{$_[0]};
  # etc
}

[download]
In fact try this: 
my $bar = ["hello", "world"];
foo($bar);
print "$bar->[0]\n";

sub foo {
  # Make my copy.
  my @foo = @{$_[0]};
  # Try to mess up the first element.
  $foo[0] =~ s/h/H/;
}

[download]
See? You get a private copy already.

In reply to RE (tilly) 2: Multiple Levels of Array Dereferencing Have me Stumped by tilly
in thread Multiple Levels of Array Dereferencing Have me Stumped by metaperl

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