pltcl broken on tcl8.5 ?

Buildfarm bobcat is broken running the pltcl regression tests - see 
http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=bobcat&dt=2008-06-15%2022:43:01

and I have reproduced this on Fedora 9 myself. This distro has Tcl 8.5.1.

I'm not sure exactly what has broken here, but I'm guessing it is 
something in the Tcl libs that has changed somehow. Has anyone been able 
to get the tests to pass using Tcl 8.5.1? Or does anyone have an idea 
about why pltcl_elog is sometimes failing to output its message?

cheers

andrew