You would mount the damaged system with the installer by doing something like:
Code:
mkdir /mnt/slack
mount /dev/hda1 /mnt/slack
Then remove the bad glibc version:
Code:
ROOT=/mnt/slack removepkg glibc-2.x.x
Finally you would mount the CD and install the correct glibc package for Slackware 11:
Code:
mkdir /mnt/cdrom
mount /dev/hdc /mnt/cdrom
installpkg -root /mnt/slack /mnt/cdrom/slackware/l/glibc-2.3.6-i486-6.tgz
Then reboot, and pray.
Note that the device notes will probably need to be adjusted for your hardware, but the basic process will remain the same.