package Tie::LazyInitialized::Hash;
use strict;

require Tie::Hash;
our @ISA = 'Tie::StdHash';

my $sub;
sub TIEHASH {
    my ($class, $callback, @args) = @_;
    $sub = sub { $callback->(@args) };
    bless {}, $class;
}
sub FETCH {
    my ($self, $key) = @_;
    %$self = %{ $sub->() } unless %$self; # hehe, i wonder if %&$sub would work?
    $self->{$key}
}

1;