Merb::Router.prepare do |r|
  r.resources :posts
  r.default_routes
  r.match('/').to(:controller => 'whatever', :action =>'index')
end


will produce this match method:

def match(request)
  params = request.params
  cached_path = request.path
  cached_method = request.method.to_s
  if  # {:path=>"^/posts/?(\\.:format)?$", :method=>"^get$"}
 (/^\/posts\/?(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2 = $1, $2) &&  (/^get$/ =~ cached_method)
    # then
    [0, {:action => "index", :format => path2, :controller => "posts"}]
  elsif  # {:path=>"^/posts/index(\\.:format)?$", :method=>"^get$"}
 (/^\/posts\/index(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2 = $1, $2) &&  (/^get$/ =~ cached_method)
    # then
    [1, {:action => "index", :format => path2, :controller => "posts"}]
  elsif  # {:path=>"^/posts/new$", :method=>"^get$"}
 (/^\/posts\/new$/ =~ cached_path)  &&  (/^get$/ =~ cached_method)
    # then
    [2, {:action => "new", :controller => "posts"}]
  elsif  # {:path=>"^/posts/?(\\.:format)?$", :method=>"^post$"}
 (/^\/posts\/?(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2 = $1, $2) &&  (/^post$/ =~ cached_method)
    # then
    [3, {:action => "create", :format => path2, :controller => "posts"}]
  elsif  # {:path=>"^/posts/:id(\\.:format)?$", :method=>"^get$"}
 (/^\/posts\/([^\/.,;?]+)(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2, path3 = $1, $2, $3) &&  (/^get$/ =~ cached_method)
    # then
    [4, {:action => "show", :format => path3, :controller => "posts", :id => path1}]
  elsif  # {:path=>"^/posts/:id[;/]edit$", :method=>"^get$"}
 (/^\/posts\/([^\/.,;?]+)[;\/]edit$/ =~ cached_path)  && (path1 = $1) &&  (/^get$/ =~ cached_method)
    # then
    [5, {:action => "edit", :controller => "posts", :id => path1}]
  elsif  # {:path=>"^/posts/:id[;/]delete$", :method=>"^get$"}
 (/^\/posts\/([^\/.,;?]+)[;\/]delete$/ =~ cached_path)  && (path1 = $1) &&  (/^get$/ =~ cached_method)
    # then
    [6, {:action => "delete", :controller => "posts", :id => path1}]
  elsif  # {:path=>"^/posts/:id(\\.:format)?$", :method=>"^put$"}
 (/^\/posts\/([^\/.,;?]+)(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2, path3 = $1, $2, $3) &&  (/^put$/ =~ cached_method)
    # then
    [7, {:action => "update", :format => path3, :controller => "posts", :id => path1}]
  elsif  # {:path=>"^/posts/:id(\\.:format)?$", :method=>"^delete$"}
 (/^\/posts\/([^\/.,;?]+)(\.([^\/.,;?]+))?$/ =~ cached_path)  && (path1, path2, path3 = $1, $2, $3) &&  (/^delete$/ =~ cached_method)
    # then
    [8, {:action => "destroy", :format => path3, :controller => "posts", :id => path1}]
  elsif  # {:path=>"/:controller(/:action(/:id)?)?(\\.:format)?"}
 (/\/([^\/.,;?]+)(\/([^\/.,;?]+)(\/([^\/.,;?]+))?)?(\.([^\/.,;?]+))?/ =~ cached_path)  && (path1, path2, path3, path4, path5, path6, path7 = $1, $2, $3, $4, $5, $6, $7)
    # then
    [9, {:action => path3 || "index", :format => path7, :controller => path1, :id => path5}]
  elsif  # {:path=>"^/$"}
 (/^\/$/ =~ cached_path)
    # then
    [10, {:action => "index", :controller => "whatever"}]
  else
    [nil, {}]
  end
end