System :: libc6
It sounds like installing libc6 is just one step on the way to installing something else - Perl? Maybe you could outline what it is that you are trying to achieve?
One issue that might be relevant is that DSL was +/- lined up with Debian Oldstable. Recently Debian Oldstable was archived, Stable became Oldstable, Unstable became Stable, etc. This might explain why, even with the libc6 extension loaded, apt-get is trying to install another libc6 - basically it is trying to install a more recent version.
original here.