How to find the packages that depend on a certain package in apt?

Another solution would be to run apt-cache rdepends libplrpc-perl.

• Why it is installed:

  aptitude why libplrpc-perl

• What depends on this package:

  aptitude search '~i~Dlibplrpc-perl'

• What would happen, if libplrpc-perl is removed:

  aptitude -s purge libplrpc-perl

Does this do what you want/need?

aptitude -v --show-summary=all-packages why <package>