As Anonymous said, you may have deleted a system directory and your system may be broken and need reinstallation. First, use 'aptitude' instead of 'apt-get', it's more advanced; aptitude and apt-get share most options. You should first try to repair the installation:

aptitude update
aptitude install -f
[download]

This should update/remove/install needed packages.

If these commands fail to set back the system to a working state, as apparently you're not a skilled Debian administrator, you must consider your system broken. You'll have to reinstall it from scratch. else you can retry to install :

aptitude install librrds-perl
[download]