title: Filter array elements with $regex
body: <pre><code> ///sample Data 
  {
      "_id" : "CUST1234",
      "Phone Number" : "9585290750",
      "First Name" : "jeff",
      "Last Name" : "ayan",
      "Email ID" : "",
      "createddate" : 1462559400000.0,
      "services" : [ 
          {
              "type" : "Enquiry",
              "timeSpent" : "0:00",
              "trxID" : "TRXE20160881",
              "CustomerQuery" : "Enquiry about travell agent numbers in basaveshwara nagara",
              "ServiceProvided" : "provided info through whatsapp",
              "Category" : "Tours/Travels",
              "callTime" : "2016-05-06T18:30:00.000Z",
              "ActualAmount" : 0,
              "FinalAmount" : 0,
              "DiscountRuppes" : 0,
              "DiscountPerctange" : 0
          }, 
          {
              "type" : "Enquiry",
              "timeSpent" : "0:00",
              "trxID" : "TRXE20160882",
              "CustomerQuery" : "Enquiry about Electric bill payment of house",
              "ServiceProvided" : "Service provided",
              "Category" : "Utility Services",
              "callTime" : "2016-05-10T18:30:00.000Z",
              "ActualAmount" : 0,
              "FinalAmount" : 0,
              "DiscountRuppes" : 0,
              "DiscountPerctange" : 0
          }, 
          {
              "type" : "Enquiry",
              "timeSpent" : "0:00",
              "trxID" : "TRXE20160883",
              "CustomerQuery" : "Enquiry about KPSC office number",
              "ServiceProvided" : "provided info through whatsapp",
              "Category" : "Govt Offices/Enquiries",
              "callTime" : "2016-05-13T18:30:00.000Z",
              "ActualAmount" : 0,
              "FinalAmount" : 0,
              "DiscountRuppes" : 0,
              "DiscountPerctange" : 0
          }, 
          {
              "type" : "Enquiry",
              "timeSpent" : "0:00",
              "trxID" : "TRXE20160884",
              "CustomerQuery" : "Enquiry about Sagara appolo hospital contact number",
              "ServiceProvided" : "provided the information through call",
              "Category" : "Hospitals/Equipments",
              "callTime" : "2016-05-14T18:30:00.000Z",
              "ActualAmount" : 0,
              "FinalAmount" : 0,
              "DiscountRuppes" : 0,
              "DiscountPerctange" : 0
          },
   ]
  }
  </code></pre>
  
  <p>Expected Output :  entire data that matches particular string in search box from "services" field.</p>
  
  <pre><code>     db.collection.aggregate([
          { 
              $match: { 
                  "Phone Number": "9585290750", 
                  "services": { $regex: "/^t/", $options: "s i" }
              }
          },                     
          {
              $project: {
                  "Services": "services" 
              }
          }
      ]);
  </code></pre>
  
  <p>I am facing an issue in regex portion in the above Collection, <code>services</code> is an array field. Please help me to filter the data.</p>