Recent work on the theme of power corrections in perturbative QCD is briefly
reviewed, with an emphasis on event shapes in e+ e- annihilation. The
factorization of soft gluon effects is the main tool: it leads to resummation,
and thus highlights the limitations of perturbation theory, pointing to
nonperturbative corrections whose size can be estimated. Power corrections can
be resummed into shape functions, for which QCD--based models are available.
Theoretical progress is closing in on the nonperturbative frontier.Comment: 15 pages, no figures. Invited talk at the XIV Italian Meeting on High
Energy Physics, Parma, April 2002. Extended versio
