file language : how to retrieve a header whose key contains DOT

Hi.
I have a header that contains the key '.' => "aphp.destination.site"
I am trying to locate a filename in a url but I can not get my header
I use camel 2.8.1

I found in the sample language syntax
${header[key]} I tried to ${header[breadcrumbId]} but it does not work
I get an error telling me that the syntax is valid
${header.name[breadcrumbId]} but it not work.

I saw that for a key with spaces must be use quotes
${header.name['key foo']} but it does not work
no more than ${header.name['breadcrumbId']}

Thank
BYE