parsley_bug.rb

require 'parslet'

tree = {:multi=>
  [{:tag=>{:name=>"Foo"}},
   {:block=>{:name=>"Foo", :multi=>[{:static=>"Bar"}]}}]}

transformer = Parslet::Transform.new do

  rule :static => simple(:text) do
    'STATIC'
  end

  rule :tag => {:name => simple(:name)} do
    'TAG'
  end

  rule :multi => subtree(:body) do
    [:multi, *body]
  end

end

p transformer.apply tree