You're right.. the best way to do this is to just check for the key's existence in the hash (perhaps factored into some function). But since you asked for a snazzy Perlish way, you could tie the hash to return a specific value when the key doesn't exist.

I was surprised not to see something that does this on CPAN. Perhaps I didn't search for the right thing. Either way, it's a pretty simple tie interface: 

package Tie::Hash::DefaultVal;
require Tie::Hash;
@ISA = qw[Tie::ExtraHash];

sub TIEHASH {
    my ($pkg, $default) = @_;
    bless [ {}, $default ], $pkg;
}

sub FETCH {
    my ($self, $key) = @_;
    exists $self->[0]{$key} ? $self->[0]{$key} : $self->[1];
}

[download]
The to use it... 
tie my %h, Tie::Hash::DefaultVal => "default-val";
%h = (
    foo => "foo-val",
    bar => "bar-val"
);

print "\$h{$_} = $h{$_}\n" for qw[ foo bar nonexistant ];

__OUTPUT__
$h{foo} = foo-val
$h{bar} = bar-val
$h{nonexistant} = default-val

[download]

blokhead

In reply to Re: Having a "default" hash value! by blokhead
in thread Having a "default" hash value! by Ace128

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