A custom processor for the Sitecore.Analytics ParseReferrer pipeline, which is able to parse keywords from url fragments (ex. https://www.google.com/#q=test)

ParseCustomSearchEngine.cs

using System;
using System.Collections.Generic;
using System.Web;
using System.Xml;

namespace Hedgehog.SitecoreExtensions.Pipelines.ParseReferrer
{
  using Sitecore.Analytics.Pipelines.ParseReferrer;
  using Sitecore.Collections;
  using Sitecore.Diagnostics;
  using Sitecore.Extensions.StringExtensions;
  using Sitecore.Xml;

  public class ParseCustomSearchEngine : ParseReferrerBaseProcessor
  {
    private readonly SafeDictionary<string, string> map = new SafeDictionary<string, string>();

    public virtual void AddHostFragmentName(XmlNode configNode)
    {
      Assert.ArgumentNotNull(configNode, "configNode");
      string hostname = XmlUtil.GetAttribute("hostname", configNode);
      string fragmentName = XmlUtil.GetAttribute("fragmentname", configNode);
      try
      {
        map[hostname] = fragmentName;
      }
      catch (Exception exception)
      {
        Log.Error("Could not register host or fragment name. Host: " + hostname + ", FragmentName: " + fragmentName, exception, this);
      }
    }

    public override void Process(ParseReferrerArgs args)
    {
      Assert.ArgumentNotNull(args, "args");
      foreach (KeyValuePair<string, string> current in map)
      {
        string key = current.Key;
        string value = current.Value;
        if (ParseKeywordsFromFragment(args, key, value))
        {
          args.AbortPipeline();
          break;
        }
      }
    }

    private bool ParseKeywordsFromFragment(ParseReferrerArgs args, string hostName, string fragmentName)
    {
      Uri urlReferrer = args.UrlReferrer;
      string dnsSafeHost = urlReferrer.DnsSafeHost;
      if (dnsSafeHost.IndexOf(hostName, StringComparison.CurrentCultureIgnoreCase) < 0)
      {
        return false;
      }

      // grab full url instead of just query string
      string text = urlReferrer.OriginalString;
      if (string.IsNullOrEmpty(text))
      {
        return false;
      }

      int fragmentIndex = text.IndexOf("#", StringComparison.InvariantCulture);
      if (fragmentIndex >= 0)
      {
        text = text.Mid(fragmentIndex + 1);
      }

      int valueStartIndex = text.IndexOf('=');
      if (valueStartIndex >= 0)
      {
        if (text.Left(valueStartIndex) == fragmentName)
        {
          string keywords = text.Mid(valueStartIndex + 1);
          string decodedKeywords = HttpUtility.UrlDecode(keywords);
          if (decodedKeywords != null)
          {
            keywords = decodedKeywords.Trim();
          }
          if (!string.IsNullOrEmpty(keywords))
          {
            args.Interaction.Keywords = keywords.ToLowerInvariant();
          }
        }
      }
      return true;
    }
  }
}