```ruby
module Garufa
  module API
    module Routes
      module Channels
        Server.route('channels') do |r|
          r.on 'channels' do

            stats = Stats.new(Subscriptions.all)

            # GET channels
            r.is do
              render 'channels', locals: { stats: stats.all_channels, filter: filter }
            end

            # GET channels/presence-channel
            r.is "presence-:channel" do |channel|
              render 'presence', locals: { stats: stats.single_channel(channel), filter: filter }
            end

            # GET channels/presence-channel/users
            r.is /(presence-.+)\/users/ do |channel|
              render 'presence_users', locals: { stats: stats.single_channel(channel) }
            end

            # GET channels/non-presence-channel
            r.is String do |channel|
              render 'non_presence', locals: { stats: stats.single_channel(channel) }
            end

            # GET channels/non-presence-channel/users
            r.is String, "users" do |channel|
              response.status = 400
              nil
            end
          end
        end
      end
    end
  end
end
```

Use %r{} notation in order to avoid warning
user
```ruby
module Garufa
  module API
    module Routes
      module Channels
        Server.route('channels') do |r|
          r.on 'channels' do

            stats = Stats.new(Subscriptions.all)

            # GET channels
            r.is do
              render 'channels', locals: { stats: stats.all_channels, filter: filter }
            end

            # GET channels/presence-channel
            r.is "presence-:channel" do |channel|
              render 'presence', locals: { stats: stats.single_channel(channel), filter: filter }
            end

            # GET channels/presence-channel/users
            r.is %r{(presence-.+)/users} do |channel|
              render 'presence_users', locals: { stats: stats.single_channel(channel) }
            end

            # GET channels/non-presence-channel
            r.is String do |channel|
              render 'non_presence', locals: { stats: stats.single_channel(channel) }
            end

            # GET channels/non-presence-channel/users
            r.is String, "users" do |channel|
              response.status = 400
              nil
            end
          end
        end
      end
    end
  end
end
```
assistant