SpamAssassin has used re2c (via sa-compile) for many years, now,
and it seems to work fine, there. GMime also looks promising
when combined with Inline::C since GMime can operate on mmap-ed
regions.
Given the inevitable demise of many .orgs when price rise;
supporting a URL rewriter similar to .mailmap makes sense.
And HTTP CONNECT seems like something our -httpd can support
to let firewalled users read over NNTP.