  In this contribution to the proceedings, we analyze the transition from
perturbative and non- perturbative QCD embedded in the coupling constant. In
the study of quark-hadron duality, we suggest that the realization of the
latter is related to the inclusion of non-perturbative effects at the level of
the coupling constant. The outcome of our analysis is a smooth transition from
perturba- tive to non-pertuperturbative QCD physics, embodied in the running of
the coupling constant at intermediate scales. While our approach is purely
perturbative, we compare our result to various non-perturbative schemes.
