use Data::Dumper;

my $ref = { "baz" => [1,2,3,4] };

print Dumper $ref;
foo($ref);
#$ref should be [1,2,3,4] now
print Dumper $ref;

sub foo {
    my $bar = shift;
    $bar = $bar->{baz}; #(1)
    #@$bar = @{$bar->{baz}}; #(2)
    print Dumper $bar;
}