my $default_action = 'dothis';
my %actions = (
               dothis           => \&do_this,
               dothat           => \&do_that,
               dosomethingelse  => \&do_something_else,
              );

my $action = param('action');
$action = $default{action} unless defined $actions{$action};
&{$actions{$action}}();