Question

I have got this part from a Perl plugin. I don’t understand what it does. Is it an array of associative arrays? If so, then shouldn’t it be started with @? Can anyone shed some light on this issue?

my $arguments =
  [ { 'name' => "process_exp",
    'desc' => "{BasePlugin.process_exp}",
    'type' => "regexp",
    'deft' => &get_default_process_exp(),
    'reqd' => "no" },
  { 'name' => "assoc_images",
    'desc' => "{MP4Plugin.assoc_images}",
    'type' => "flag",
    'deft' => "",
    'reqd' => "no" },
  { 'name' => "applet_metadata",
    'desc' => "{MP4Plugin.applet_metadata}",
    'type' => "flag",
    'deft' => "" },
  { 'name' => "metadata_fields",
    'desc' => "{MP4Plugin.metadata_fields}",
    'type' => "string",
    'deft' => "Title,Artist,Genre" },
  { 'name' => "file_rename_method",
    'desc' => "{BasePlugin.file_rename_method}",
    'type' => "enum",
    'deft' => &get_default_file_rename_method(), # by default rename imported files and assoc files using this encoding
    'list' => $BasePlugin::file_rename_method_list,
    'reqd' => "no"
  } ];

Answer 1

As Bwmat said it’s a reference to an Array of Hash references. Read

$ man perlref

or

$ man perlreftut     # this is a bit more straightforward

for if you want to know more about references.

By the way in fiew words in Perl you can do:

@array = ( 1, 2 );          # declare an array
$array_reference = \@array; # take the reference to that array
$array_reference->[0] = 2;  # overwrite 1st position of @array

$numbers = [ 3, 4 ];        # this is another valid array ref declaration. Note [ ] instead of ( )

the same thing happens with hashes.

By the way in fiew words in Perl you can do:

%hash = ( foo => 1, bar => 2 );
$hash_reference = \%hash; 
$hash_reference->{foo} = 2;

$langs = { perl => 'cool', php => 'ugly' }; # this is another valid hash ref declaration. Note { } instead of ( )

And… yes, you can dereference these references.

%{ $hash_reference }

will be treated as it was a hash, so if you want to print the keys of $langs above, you can do:

print $_, "\n" foreach ( keys %{ $langs } );

To dereference an array ref use @{ } instead of %{ }. Even sub can be dereferenced.

sub foo
{
  print "hello world\n";
}

my %hash = ( call => \&foo );

&{ $hash{call} }; # this allows you to call the sub foo