http://www.perlmonks.org?node_id=684069


in reply to Default Hash Key

It can also be done using a tied hash (with a speed penalty). I don't see an existing module on CPAN after a quick look, but it's it's easy to write your own.
{ package Hash::WithDefault; use Tie::Hash qw( ); BEGIN { our @ISA = 'Tie::ExtraHash'; } use constant IDX_HASH => 0; use constant IDX_DEFAULT => 1; use constant NEXT_IDX => 2; sub FETCH { my ($self, $key) = @_; return ( exists( $self->[IDX_HASH]{$key} ) ? $self->[IDX_HASH]{$key} : $self->[IDX_DEFAULT] ); } } { tie my %hash, 'Hash::WithDefault', 'not in the alphabet'; %hash = ( a => 'a vowel', b => 'a consonant', ); print("$_: $hash{$_}\n") for qw( a b ~ ); }

Output:

a: a vowel b: a consonant ~: not in the alphabet