How do I copy an array using a reference in Perl?

Question

If I do the following, it works fine:

print $ref->{element}->[0]->{data};

I would like to see how many references are in the array so that I can loop through them, but I am having a hard time doing that.

Here is the code I have tried, but it doesn't work:

my @array = @$ref->{element};

foreach(@array) {
    print $_->{data};
}

I get an "Not an ARRAY reference" error

Answer 1

As a general aid in debugging, give Data::Dumper a look. It's invaluable for poking about in the innards of data structures.

Answer 2

Hashes of lists are tricky that way. @$ref->{element} gets parsed as (@$ref)->{element}, dereferencing $ref instead of $ref->{element}.

Try

my @array = @{$ref->{element}}

or

my $size = scalar @{$ref->{element}}

Gory details in perllol.

Answer 3

In addition to the @mobrule answer:

You can also shorten the expression a bit by omitting the '->' operator (good for long expressions):

print $ref->{element}[0]{data};

and

my @array = @{$$ref{element}};