title: how to pass strings to functions not by ref (Ruby)
body: <p>Check following code</p>
  
  <pre><code>def wipe_mutterings_from( sentence )
     while sentence.include? '('
       open = sentence.index( '(' )
       close = sentence.index( ')', open )
       sentence[open..close] = '' if close
     end
  end
  
  foo='abbba (jjjj) kkkkkk'
  wipe_mutterings_from( foo )
  p foo
  </code></pre>
  
  <p>In my understanding I have passed the string by ref to the function (much like is done in lower level languages like c/cpp).<br>
  Is it possible to pass the string only by value (like in PHP)?<br>
  I am fully aware I can duplicate the string inside the function and work only on the copy.</p>