module Haml::Precompiler

def rstrip_buffer!

or the merged text
Get rid of and whitespace at the end of the buffer 
def rstrip_buffer!
  unless @merged_text.empty?
    @merged_text.rstrip!
  else
    push_silent("_erbout.rstrip!", false)
    @dont_tab_up_next_text = true
  end
end