Another approach is to use a named sub - all the examples of Dancer code tend to use anonymous subs, but there's nothing that says it has to be anonymous.
get '/users' => \&show_users;
get '/users/:id' => \&show_users;
sub show_users
{
#Do something
}
Note that, due to the way Dancer does the route matching, this is order-dependent and, in my experience, I've had to list the routes with fewer elements first.