As I suspected, this was not a Parrot problem. diakopter provided the diagnosis on IRC: In April, Debian re-classified Sarge (3.1) as "oldstable" and Etch (4.0) as stable. My /etc/apt/sources.list simply pointed to "stable" to get packages. So when I requested the flex upgrade, it got that package, along with dependent packages, from the Etch repository rather than Sarge. The glibc I got from there would not work with Sarge.
The treatment was to upgrade from Sarge to Etch. Since I'm working with a Linux virtual machine (linode.com) rather than my own server, I approached this with some trepidation; I'd never done that big an upgrade before. Fortunately I got help on #linode and #debian on the OFTC network (irc.oftc.net) from users matt_, npmr, miksuh and gsimmons. I followed the Debian release notes (http://www.debian.org/releases/stable/i386/release-notes/ap-old-stuff.en.html) as to making backups, etc., and then hit the magic button. Once my server was upgraded, I reconfigured and re-ran 'make': successfully. Closing ticket. kid51
