Data::Dumper

#!/usr/bin/perl
use strict;
use warnings;

use Data::Dumper ();

my $data_structure = {
    phones => {
        Foo     => 123, 
        Bar     => 345,
        Baz     => 678,
    }
};

open my $fh, '>', 'dumped.data' or die;
print $fh Data::Dumper->Dump([$data_structure], ['data_structure']);
close $fh;

$data_structure = {
                    'phones' => {
                                  'Bar' => 345,
                                  'Baz' => 678,
                                  'Foo' => 123
                                }
                  };

#!/usr/bin/perl
use strict;
use warnings;

my $data_structure;
my $filename = 'dumped.data';
if (open my $fh, '<', $filename) {
    local $/ = undef;
    my $dump = <$fh>;
    eval $dump;
} else {
    die "Could not open '$filename' $!";
}

print "Foo: $data_structure->{phones}{Foo}\n"; # Foo: 123
print "Bar: $data_structure->{phones}{Bar}\n"; # Bar: 345
print "Baz: $data_structure->{phones}{Baz}\n"; # Baz: 678