sub getByKey {
    my $key = shift;
    my $idx = $indexOf{ $key };
    my $value = $actual[ $idx ];
    push @actual, splice @actual, $idx, 1;
    push @keyFor, splice @keyFor, $idx, 1;
    
    ## Completely re-build %indexOf
    $indexOf{ $keyFor[ $_ ] } = $_ for 0 .. $#keyFor;
    
    return $value
}