Capture cookie and set as header

Sorry if this is a repeat. I sent last week but never saw it come into my inbox (Will I see my own messages come in on the list?) so I'm not sure it made it to the list. I need to capture a cookie value in a request and then append it as a http header value. I've been searching for examples for

Capture cookie as set as header

I've been asked if I can use haproxy to capture a cookie value and set it as a header value. I know how to set headers and I see docs on capturing cookies to the log but that's as far as I get. Is this possible? If so any examples? MG