Programming the Perl DBI

The Storable Module

In addition to Data::Dumper, there are other data marshalling modules available that you might wish to investigate, including the fast and efficient Storable.

The following code takes the same approach as the example we listed for Data::Dumper to show the basic store and retrieve cycle:

#!/usr/bin/perl -w
#
# ch02/marshal/storabletest: Create a Perl hash and store it externally. Then, 
#                            we reset the hash and reload the saved one.

use Storable qw( freeze thaw );

### Create some values in a hash
my $megalith = {
    'name' => 'Stonehenge',
    'mapref' => 'SU 123 400',
    'location' => 'Wiltshire',
};

### Print them out
print "Initial Values:   megalith = $megalith->{name}\n" .
      "                  mapref   = $megalith->{mapref}\n" .
      "                  location = $megalith->{location}\n\n";

### Store the values to a string
my $storedValues = freeze( $megalith );

### Reset the variables to rubbish values
$megalith = {
    'name' => 'Flibble Flabble',
    'mapref' => 'XX 000 000',
    'location' => 'Saturn',
};

### Print out the rubbish values
print "Rubbish Values:   megalith = $megalith->{name}\n" .
      "                  mapref   = $megalith->{mapref}\n" .
      "                  location = $megalith->{location}\n\n";

### Retrieve the values from the string
$megalith = thaw( $storedValues );

### Display the re-loaded values
print "Re-loaded Values: megalith = $megalith->{name}\n" .
      "                  mapref   = $megalith->{mapref}\n" .
      "                  location = $megalith->{location}\n\n";

exit;

This program generates the following output, which illustrates that we are storing data persistently then ...