  Modern advances in particle physics depend strongly on the usage of reliable
computer programs. In this context two issues become important: The usage of
powerful algorithms to handle the amount of evaluated data properly, and a
software architecture capable to overcome the problems of maintainability and
extendability. We present our approach to such a computer program, called
tapir. This tool assists computations in perturbative quantum field theory in
many ways. Such calculations often involve the evaluation of a large amount of
Feynman diagrams with multiple loops. tapir helps in reducing the number of
diagrams, and the resulting integrals thereof, by identifying and minimizing
their topological structure. We will focus on a three-loop calculation which is
needed for the next-to-next-to leading order predictions of neutral $B$-meson
systems. We show how tapir can be utilized for this kind of calculation.
