How do I determine the number of elements in an array reference?

Here is the situation I am facing...

$perl_scalar = decode_json( encode ('utf8',$line));

decode_json returns开发者_运维知识库 a reference. I am sure this is an array. How do I find the size of $perl_scalar?? As per Perl documentation, arrays are referenced using @name. Is there a workaround?

This reference consist of an array of hashes. I would like to get the number of hashes.

If I do length($perl_scalar), I get some number which does not match the number of elements in array.

That would be:

scalar(@{$perl_scalar});

You can get more information from perlreftut.

You can copy your referenced array to a normal one like this:

my @array = @{$perl_scalar};

But before that you should check whether the $perl_scalar is really referencing an array, with ref:

if (ref($perl_scalar) eq "ARRAY") {
  my @array = @{$perl_scalar};
  # ...
}

The length method cannot be used to calculate length of arrays. It's for getting the length of the strings.

You can also use the last index of the array to calculate the number of elements in the array.

my $length = $#{$perl_scalar} + 1;

$num_of_hashes = @{$perl_scalar};

Since you're assigning to a scalar, the dereferenced array is evaluated in a scalar context to the number of elements.

If you need to force scalar context then do as KARASZI says and use the scalar function.

You can see the entire structure with Data::Dumper:

use Data::Dumper;
print Dumper $perl_scalar;

Data::Dumper is a standard module that is installed with Perl. For a complete list of all the standard pragmatics and modules, see perldoc perlmodlib.