High-energy QCD: Interplay of nonperturbative and perturbative effects

Soft interaction is an unavoidable participant of every hard process at high energies. Although the factorisation theorems allow to separate the hard and soft parts of the interaction, in many instances (not covered by the theorems) factorisation is broken, and the processes are dominated by the interplay between the perturbative and nonperturbative effects. Several examples are overviewed in this note.