just a little contribution to this instructive thread..
Have you read Of Symbol Tables and Globs by broquaint? You'll find very interesting.

The final comment of the article says:

So in summary, symbol tables store globs and can be treated like hashes. Globs are accessed like hashes and store references to the individual data types. I hope you've learned something along the way and can now go forth and munge these two no longer mysterious aspects of perl with confidence!

Typeglobs are used in many magic use of Perl as in Using the DATA file handle for ARGV
HtH
L*