  The dispersive approach to QCD, which properly embodies the intrinsically
nonperturbative constraints originating in the kinematic restrictions on
relevant physical processes and extends the applicability range of perturbation
theory towards the infrared domain, is briefly overviewed. The study of OPAL
(update 2012) and ALEPH (update 2014) experimental data on inclusive tau lepton
hadronic decay in vector and axial-vector channels within dispersive approach
is presented.
