Understanding Data::Dumper output - perl

Question

Simple question:
use warnings;
use XML::Simple;
use Data::Dumper;
my $file='test.osm';
my $test_data = XMLin( $file );
print Dumper( $test_data );
my #way_node_refs=$test_data->{'way'}->{'nd'};
print Dumper( #way_node_refs );
print( #way_node_refs[1]->{'ref'} );ere
It has the following output. The first dump is not given because it does not matter.
$VAR1 = [
{
'ref' => '453966480'
},
{
'ref' => '453966490'
},
{
'ref' => '453966482'
},
{
'ref' => '453966130'
},
{
'ref' => '453966143'
},
{
'ref' => '453966480'
}
];
How can I access the values with the key ref. I don't know how to interprete the braces kinda.

Answer 1

This is called array of hashes. If $array contains the data then below will work :
[] is anonymous array reference, while {} is anonymous hash reference. Check perlref.
for (#{ $array }) {
print $_ -> {ref},"\n";
}
Further reading:
Using Arrow operator(->) - Most suitable for accesing a single item from arrayref or hashref.
Using # { } - Suitable for iterating over arrayrefs .
Edit:
Now after your edit, it is clear that you want something like this:
for (#way_node_refs) {
print $_ -> {ref},"\n";
}

Answer 2

You have an array reference where the values inside the array are hash references. To access single values, use the arrow operator ->.
print $foo->[0]->{ref};
print $foo->[1]->{ref};
Or you can loop through them.
foreach my $elem ( #{ $foo } ) {
print Dumper $elem;
print $elem->{ref};
}
You could even sort them alphabetically by the values of the ref keys.
my #sorted = sort { $a->{ref} cmp $b->{ref} } #$foo; # note #sorted is an array
See perlref, perlreftut and perldsc for more details on data structures and references.