injecting small piece of html into pages retrieved

["Edward Rosinzonsky" <erosin@xxxxxxxxx>]

Hi,

I'd like to inject a small piece of HTML into any page retrieved
through the proxy. E.g. change "</head>" to "<script ...></head>".
The HTML is static.  That is the same piece of HTML is to be injected
into every page.  Is this possible?  If so, how?  Is there perhaps a
plugin, that could make this possible?

Thanks.