title: How to access standard string manipulation functions in Lua?
body: <p>I need some basic string operations, like sub-string, find string in string etc. I found a documentation of some standard functions for that: <a href="http://www.lua.org/manual/2.4/node22.html" rel="nofollow">http://www.lua.org/manual/2.4/node22.html</a></p>
  
  <p>But when I try it, I get an error:</p>
  
  <pre><code>input:29: attempt to call a nil value (global 'strfind')
  </code></pre>
  
  <p>Do I have to use <code>require</code>? Or are those methods contained in some object?</p>