You need a modified dispatch table. A dispatch table is where you have (generally) a hash of names where the values are references to subroutines.

my %dispatch = (
    foo => sub { print "foo\n"; },
    bar => \&bar,
);

chomp( my $input = <> );
unless ( exists $dispatch{ $input } ) {
    die "I don't know what to do with '$input'\n";
}
$dispatch{$input}->();

sub bar { print "bar\n"; }
[download]

The modification needed is that you aren't matching on a simple string. There's a few ways to improve this. One is to pass $family to every function and let them determine if they want to handle it. Then, the function returns either true (I handled it) or false (I don't deal with this value). Errors would be propagated with die and caught with an eval-block.

Then, whenever you add something, you're working with a much smaller piece of the puzzle because the engine and the parts are separated.