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

##</code><code>##

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

##</code><code>##

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/;
}