my($favorite_color) = ''; # get some kind of input here

my $action = {
      'red'    => sub { 'the color is red.'    },
      'yellow' => sub { 'the color is yellow.' },
      'blue'   => sub { 'the color is blue.'   },
}->{$favourite_color} || sub { 'I do not know that color' };

print $action->();