If this is for debugging then Data::Dumper or one of its variants are good.

Otherwise you could try Data::Walk, which lets you walk over the nodes of a complex structure.

Update - Actually I don't see a way to obtain the current key/index using Data::Walk, so this is probably not an appropriate solution for you.

I don't recommend this, but just so you can see how you can do it:

for (sort keys %hash) {
    print "$_ => ";

    if (ref($hash{$_}) eq 'ARRAY') {
        print join(', ', @{ $hash{$_} });
    }
    elsif (ref($hash{$_}) eq 'HASH') {
        # do something else
    }
    else {
        print $hash{$_};
    }

    print "\n";
}
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Consider:

use strict;
use warnings;
use Tk;

my $mw = MainWindow->new (-title => 'Hello World');

my @arr=('first', 'second', 'third');
my %hash = (A => 100, B => 200, C => [@arr], D => \&hi, E => $mw);

$hash{'A'}=100;
$hash{'B'}=200;
$hash{'C'}=[@arr];

for (sort keys %hash) {
    print "$_ => ";

    if (ref($hash{$_}) eq 'ARRAY') {
        print "Array: ", join(', ', @{ $hash{$_} });
    }
    elsif (ref($hash{$_}) eq 'HASH') {
        # do something else
        print "Hash: ...";
    }
    else {
        print "Scalar: $hash{$_}";
    }

    print "\n";
}

sub hi {
    print "hello World";
}
[download]

Prints:

A => Scalar: 100
B => Scalar: 200
C => Array: first, second, third
D => Scalar: CODE(0x21bdf50)
E => Scalar: MainWindow=HASH(0x21d97ac)
[download]

Adding:

    elsif (ref($hash{$_})) {
        print "Unknown ref: $hash{$_}";
[download]

alters the output to:

A => Scalar: 100
B => Scalar: 200
C => Array: first, second, third
D => Unknown ref: CODE(0x21be538)
E => Unknown ref: MainWindow=HASH(0x21d9e38)
[download]

References come in many flavours. There is probably no good general answer to OP's question for "display" output (as opposed to debugging output), but at least unhandled cases can be caught by noting that ref returns undef for non-reference values.

---

DWIM is Perl's answer to Gödel

Re: How can I visualize my complex data structure? might give you some ideas. One of the nodes I reference therein, Re: I've got a hash of hashes how do i get my values out, will show you how to recursively access every element in a complex data structure. This might be exactly what you want.

HTH,

if (ref($hash{$_}) eq 'ARRAY')

I dont understand this.. Does the word 'ARRAY' have a special meaning in this context? What more such special words are there, and where is it possible to read about this? Appearently it does not work to write 'array' in lc.

The reason that 'array' doesn't match is that you are comparing the return value of ref with the string 'array'. ref returns what sort of reference something is, and in the case of arrays that string is 'ARRAY'

See ref for more information.

ref returns the following values:
• SCALAR
• ARRAY
• HASH
• CODE
• REF
• GLOB
• LVALUE
And it those that you must test for - depending on what you are looking for.