# File lib/rcodetools/completion.rb, line 11
  def fill_literal!(expr)
    [ "\"", "'", "`" ].each do |q|
      expr.gsub!(/#{q}(.+)#{q}/){ '"' + "x"*$1.length + '"' }
    end
    expr.gsub!(/(%([wWqQxrs])?(\W))(.+?)\3/){
      percent = $2 == 'x' ? '%'+$3 : $1 # avoid executing shell command
      percent + "x"*$4.length + $3
    }
    [ %w[( )], %w[{ }], %w![ ]!, %w[< >] ].each do |b,e|
      rb, re = [b,e].map{ |x| Regexp.quote(x)}
      expr.gsub!(/(%([wWqQxrs])?(#{rb}))(.+)#{re}/){
        percent = $2 == 'x' ? '%'+$3 : $1 # avoid executing shell command
        percent + "x"*$4.length + e
      }
    end
  end