my %dispatch = ('foo_1' => \&bar,
                'foo_2' => \&foo_2,
                'bar_3' => \&foo_2,
                'bar_4' => \&foo_2,
                'blah_5' => \&foo_2,
                'default' => \&default,
               );
(defined $dispatch{$value}) 
   ? &{$dispatch{$value}}()
   : &{$dispatch{'default'}}();