title: "eager" regexp matching
body: <p>I have to remove the string between two delimiters, i.e
  From "123XabcX321" I want "123321".
  For a simple case, I'm fine with:</p>
  
  <pre><code>$_=&lt;&gt;;
  s/X(.*)X//;
  print;
  </code></pre>
  
  <p>But if there's ambiguity in the input like "123XabcXasdfjXasdX321", it matches the first X with the last X and I get "123321" but I want "123asdfj321". 
  Is there a way to specify an "eager" match that matches with the first valid possible delimiter and not the last?</p>