As for using a hash as a backing store but only using 1 key, its only a little wasteful if there are never more than one of these objects around, and its flexible when/if you ever need to add more fields/properties.

Its a little more efficient to make $self a blessed reference to an array.

I'm not sure about blessing a reference to your tied hash but you could try it. I tend to think that would be dangerous as the creation of your backing store is then out of your hands, or at least not where a reader might expect it to be.

If you're sure you'll never need more than one field in your class, you can bless a reference to a scalar. That scalar can in turn be a reference to your tied hash. It seems a little silly if there aren't many of these objects, but probably is a little more efficient than having a hash with one key.

#!/usr/bin/perl -w

package Testing;

sub new {
  my $class = shift;
  my $ref = shift;
  my $self = \$ref;
  bless $self, $class;
}

sub get {
  my $self = shift;
  ${$self}->{shift()};
}

package main;

my %h = (one => 1, two => 2);

my $t = Testing->new(\%h);

print $t->get($_)."\n" for qw(one two);
[download]