Thanks again, excelent explanation.

But I don't see relation between these two tasks: assurance in unique module names and access to modules. For example, search.cpan.org use different way for accessing modules because it doesn't show Smart::Comment on http://search.cpan.org/~autrijus/ (there no 0.01 version of Smart::Comments on search.cpan.org at all) but show all Conway's versions.

Anyway, thanks again for your answers. Situation is now clear for me: problem with Smart::Comments and CPAN.pm has deep roots in CPAN architecture which nobody will try to fix until Perl6. :) It's easy to workaround this issue by using manually prepared module list from CPAN's directory listings, but this may result in some other unusual bugs.