title: putting '%' in string.gsub() in Lua
body: <p>i have this code</p>
  
  <pre><code>local strs = "my dog"
  print (string.gsub( strs , " ","%20"))
  </code></pre>
  
  <p>i just wanted the output will be like this <code>my%20dog</code> but i got this error </p>
  
  <pre><code>Runtime error
          ... invalid capture index
  stack traceback:
          [C]: ?
          [C]: in function 'gsub'
  </code></pre>
  
  <p>i have read that <code>%</code> is escape in Lua.</p>
  
  <p>my question is, how can i apply <code>%</code> for my replaced new string (<code>strs</code>)?</p>