When you check the existence of or retrieve an object that has a .metapairs annotation containing well-formed XML, the response headers include x-amz-meta- headers with property/value pairs that correspond to the XML elements in the annotation. The property names in these headers are the element names with the initial meta- removed.
An element with comma-separated values is returned as a single x-amz-meta- header with comma-separated values. Here’s an example that shows an XML element with comma-separated values and the x-amz-meta- header that results from that element:
<meta-author>
<![CDATA[P.D. Grey,Morgan White,Paris Black]]>
</meta-author>
x-amz-meta-author:P.D. Grey,Morgan White,Paris Black