Tie::Proxy::Hash 1.01

Tie::Proxy::Hash is a Perl module created to efficiently merge & translate hashes.

SYNOPSIS

my (%hash, $ref);
$ref = tie %hash, Tie::Proxy::Hash, (bart => +{a => 1,
b => 2},
maggie => +{a => 5,
c => 6,
e => 10},
);
$hash{a} == 1; # true
$hash{b} == 2; # true (bart supercedes maggie)
$hash{c} == 6; # true
! defined $hash{d}; # true
$hash{e} == 10; # true

$hash{c} = 9; # set in maggie
$hash{d} = 12; # set in default
$hash{f} = 11; # set in default

$ref->add_hash(lisa, +{d => 3, b => 4});
$hash{c} == 9; # true
$hash{b} == 2; # true (bart overrides lisa)
$hash{d} == 3; # true (lisa overrides default)
$hash{f} == 11; # true (only default knows f)

Proxy hash requests for one or more other hashes, with intermediate value translation.

Tie::Proxy::Hash merges hashes by maintaining a list of hashes to look up, and each key requested is looked up in each hash in order until a hit is found. Resultant values may be subject to a translating subr. In this way, hashes may be merged without the cost of by-value copying.

A default backing hash is provided to store values not present in other hashes.

Tying

$ref = tie %hash, Tie::Proxy::Hash,
bart => +{a => 1, b => 2},
maggie => +{a => 5, c => 6, e => 10} => sub {10*$_[0]},
;

Any arguments passed to tie are palmed off onto add_hash.

Retrieving Values

Values are retrieved by checking each hash in the order of insertion; the first hash found in which a given key exists supplies the value. The value is subject to translation if the given hash has an associated translator.