title: Regex match any string that isn't preceded by another string
body: <p>I suck at regex and I've been trying to get through this problem.
  The problem is that I have a string and I want to match <strong>any</strong> "+" or "-" that aren't preceded by a "^".</p>
  
  <p>Example string:</p>
  
  <pre><code>100x^-3+2x-10
  </code></pre>
  
  <p>The string above would be mathematically formatted or read as "one hundred times x to the -3 power, plus two times x, minus ten".</p>
  
  <p>And I want to match the "+" before "2x" and the "-" before the "10" but <strong>not</strong> the "-" after "100x^". I hope it's not that confusing. I have tried the following reg, with no luck:</p>
  
  <pre><code>[^\^][\+|\-]
  </code></pre>
  
  <p>Obviously I'm missing a big detail somewhere.</p>