Sinatra named regexp groups of Ruby 1.9 to name keys in params.

sinatra.rb

get %r{^/users/(?<nickname>\w+)/posts/(?<slug>[\w-]+)\.(?<extension>\w+)$} do
  p params[:nickname]
end

test.rb

path = "/users/botanicus/posts/hello-world.html"

path.match(%r{^/users/(\w+)/posts/([\w-]+)\.(\w+)$})
# => #<MatchData "/users/botanicus/posts/hello-world.html" 1:"botanicus" 2:"hello-world" 3:"html">

path.match(%r{^/users/(?<nickname>\w+)/posts/(?<slug>[\w-]+)\.(?<extension>\w+)$})
# => #<MatchData "/users/botanicus/posts/hello-world.html" nickname:"botanicus" slug:"hello-world" extension:"html">
# => Use params[:nickname], params[:slug] etc.