Adding meta tags to page headers

[Ulf Dittmer]

If I wanted to add meta tags to the page header (specifically, description,
keywords and robots), would I have to write a plugin or a filter? With a
plugin I can pass the values of those headers along, but I don't think
plugins have access (or can add) tags to the HTML header...? With a
post-translate filter that would be possible, but it would be kind of messy
to have to work with the raw HTML in order to add tags. Am I missing some
other approach of controlling HTML headers?