php - mthaml Illegal nesting: nesting within echo is illegal

I need to execute the following haml

  = form_open('login', array('method' => 'POST'))
    %p
      %label{:for => "password"} Password
      = form_input($login_password)
    %p
      %input{:name => "submit", :type => "submit", :value => "Login"}
  = form_close()
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But I keep getting

with message 'Illegal nesting: nesting within echo is illegal in 
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I understand the error and that it's nested but how do i fix it? It worked fine with the other php library called phamlp