title: Prevent bash from adding single quotes to variable output
body: <p><strong>Problem:</strong>
  I'm writing a script that performs several HTTP requests with <code>curl</code> and I want to add the headers to a variable, <code>CURL_HEADERS</code>, so that I don't have to type them out constantly. When I echo the <code>CURL_HEADERS</code> variable in the curl command, single quotations appear where I don't want them. How can I prevent this? (The code below is simplified for the sake of clarity)</p>
  
  <p><strong>Code</strong></p>
  
  <pre><code>#!/usr/bin/env bash
  AUTH_KEY='1234'
  set -x
  CURL_HEADERS='-H "Authorization: Basic '${AUTH_KEY}'" -H "Content-Type: application/json"'
  echo "${CURL_HEADERS}"
  curl -s $(echo "${CURL_HEADERS}") 'http://www.example.org' &gt; /dev/null
  set +x
  </code></pre>
  
  <p><strong>Expected Output:</strong></p>
  
  <pre><code>+ CURL_HEADERS='-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  + echo '-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  -H "Authorization: Basic 1234" -H "Content-Type: application/json"
  ++ echo '-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  + curl -s -H "Authorization: Basic 1234" -H "Content-Type: application/json" http://www.example.org
  + set +x
  </code></pre>
  
  <p><strong>Actual Output</strong></p>
  
  <pre><code>+ CURL_HEADERS='-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  + echo '-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  -H "Authorization: Basic 1234" -H "Content-Type: application/json"
  ++ echo '-H "Authorization: Basic 1234" -H "Content-Type: application/json"'
  + curl -s -H '"Authorization:' Basic '1234"' -H '"Content-Type:' 'application/json"' http://www.example.org
  + set +x
  </code></pre>